| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
| * |
| * Swap reorganised 29.12.95, Stephen Tweedie. |
| * kswapd added: 7.1.96 sct |
| * Removed kswapd_ctl limits, and swap out as many pages as needed |
| * to bring the system back to freepages.high: 2.4.97, Rik van Riel. |
| * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). |
| * Multiqueue VM started 5.8.00, Rik van Riel. |
| */ |
| |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/mm.h> |
| #include <linux/sched/mm.h> |
| #include <linux/module.h> |
| #include <linux/gfp.h> |
| #include <linux/kernel_stat.h> |
| #include <linux/swap.h> |
| #include <linux/pagemap.h> |
| #include <linux/init.h> |
| #include <linux/highmem.h> |
| #include <linux/vmpressure.h> |
| #include <linux/vmstat.h> |
| #include <linux/file.h> |
| #include <linux/writeback.h> |
| #include <linux/blkdev.h> |
| #include <linux/buffer_head.h> /* for buffer_heads_over_limit */ |
| #include <linux/mm_inline.h> |
| #include <linux/backing-dev.h> |
| #include <linux/rmap.h> |
| #include <linux/topology.h> |
| #include <linux/cpu.h> |
| #include <linux/cpuset.h> |
| #include <linux/compaction.h> |
| #include <linux/notifier.h> |
| #include <linux/delay.h> |
| #include <linux/kthread.h> |
| #include <linux/freezer.h> |
| #include <linux/memcontrol.h> |
| #include <linux/migrate.h> |
| #include <linux/delayacct.h> |
| #include <linux/sysctl.h> |
| #include <linux/memory-tiers.h> |
| #include <linux/oom.h> |
| #include <linux/pagevec.h> |
| #include <linux/prefetch.h> |
| #include <linux/printk.h> |
| #include <linux/dax.h> |
| #include <linux/psi.h> |
| #include <linux/pagewalk.h> |
| #include <linux/shmem_fs.h> |
| #include <linux/ctype.h> |
| #include <linux/debugfs.h> |
| #include <linux/khugepaged.h> |
| #include <linux/rculist_nulls.h> |
| #include <linux/random.h> |
| |
| #include <asm/tlbflush.h> |
| #include <asm/div64.h> |
| |
| #include <linux/swapops.h> |
| #include <linux/balloon_compaction.h> |
| #include <linux/sched/sysctl.h> |
| |
| #include "internal.h" |
| #include "swap.h" |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/vmscan.h> |
| |
| struct scan_control { |
| /* How many pages shrink_list() should reclaim */ |
| unsigned long nr_to_reclaim; |
| |
| /* |
| * Nodemask of nodes allowed by the caller. If NULL, all nodes |
| * are scanned. |
| */ |
| nodemask_t *nodemask; |
| |
| /* |
| * The memory cgroup that hit its limit and as a result is the |
| * primary target of this reclaim invocation. |
| */ |
| struct mem_cgroup *target_mem_cgroup; |
| |
| /* |
| * Scan pressure balancing between anon and file LRUs |
| */ |
| unsigned long anon_cost; |
| unsigned long file_cost; |
| |
| #ifdef CONFIG_MEMCG |
| /* Swappiness value for proactive reclaim. Always use sc_swappiness()! */ |
| int *proactive_swappiness; |
| #endif |
| |
| /* Can active folios be deactivated as part of reclaim? */ |
| #define DEACTIVATE_ANON 1 |
| #define DEACTIVATE_FILE 2 |
| unsigned int may_deactivate:2; |
| unsigned int force_deactivate:1; |
| unsigned int skipped_deactivate:1; |
| |
| /* Writepage batching in laptop mode; RECLAIM_WRITE */ |
| unsigned int may_writepage:1; |
| |
| /* Can mapped folios be reclaimed? */ |
| unsigned int may_unmap:1; |
| |
| /* Can folios be swapped as part of reclaim? */ |
| unsigned int may_swap:1; |
| |
| /* Not allow cache_trim_mode to be turned on as part of reclaim? */ |
| unsigned int no_cache_trim_mode:1; |
| |
| /* Has cache_trim_mode failed at least once? */ |
| unsigned int cache_trim_mode_failed:1; |
| |
| /* Proactive reclaim invoked by userspace through memory.reclaim */ |
| unsigned int proactive:1; |
| |
| /* |
| * Cgroup memory below memory.low is protected as long as we |
| * don't threaten to OOM. If any cgroup is reclaimed at |
| * reduced force or passed over entirely due to its memory.low |
| * setting (memcg_low_skipped), and nothing is reclaimed as a |
| * result, then go back for one more cycle that reclaims the protected |
| * memory (memcg_low_reclaim) to avert OOM. |
| */ |
| unsigned int memcg_low_reclaim:1; |
| unsigned int memcg_low_skipped:1; |
| |
| /* Shared cgroup tree walk failed, rescan the whole tree */ |
| unsigned int memcg_full_walk:1; |
| |
| unsigned int hibernation_mode:1; |
| |
| /* One of the zones is ready for compaction */ |
| unsigned int compaction_ready:1; |
| |
| /* There is easily reclaimable cold cache in the current node */ |
| unsigned int cache_trim_mode:1; |
| |
| /* The file folios on the current node are dangerously low */ |
| unsigned int file_is_tiny:1; |
| |
| /* Always discard instead of demoting to lower tier memory */ |
| unsigned int no_demotion:1; |
| |
| /* Allocation order */ |
| s8 order; |
| |
| /* Scan (total_size >> priority) pages at once */ |
| s8 priority; |
| |
| /* The highest zone to isolate folios for reclaim from */ |
| s8 reclaim_idx; |
| |
| /* This context's GFP mask */ |
| gfp_t gfp_mask; |
| |
| /* Incremented by the number of inactive pages that were scanned */ |
| unsigned long nr_scanned; |
| |
| /* Number of pages freed so far during a call to shrink_zones() */ |
| unsigned long nr_reclaimed; |
| |
| struct { |
| unsigned int dirty; |
| unsigned int unqueued_dirty; |
| unsigned int congested; |
| unsigned int writeback; |
| unsigned int immediate; |
| unsigned int file_taken; |
| unsigned int taken; |
| } nr; |
| |
| /* for recording the reclaimed slab by now */ |
| struct reclaim_state reclaim_state; |
| }; |
| |
| #ifdef ARCH_HAS_PREFETCHW |
| #define prefetchw_prev_lru_folio(_folio, _base, _field) \ |
| do { \ |
| if ((_folio)->lru.prev != _base) { \ |
| struct folio *prev; \ |
| \ |
| prev = lru_to_folio(&(_folio->lru)); \ |
| prefetchw(&prev->_field); \ |
| } \ |
| } while (0) |
| #else |
| #define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0) |
| #endif |
| |
| /* |
| * From 0 .. MAX_SWAPPINESS. Higher means more swappy. |
| */ |
| int vm_swappiness = 60; |
| |
| #ifdef CONFIG_MEMCG |
| |
| /* Returns true for reclaim through cgroup limits or cgroup interfaces. */ |
| static bool cgroup_reclaim(struct scan_control *sc) |
| { |
| return sc->target_mem_cgroup; |
| } |
| |
| /* |
| * Returns true for reclaim on the root cgroup. This is true for direct |
| * allocator reclaim and reclaim through cgroup interfaces on the root cgroup. |
| */ |
| static bool root_reclaim(struct scan_control *sc) |
| { |
| return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_mem_cgroup); |
| } |
| |
| /** |
| * writeback_throttling_sane - is the usual dirty throttling mechanism available? |
| * @sc: scan_control in question |
| * |
| * The normal page dirty throttling mechanism in balance_dirty_pages() is |
| * completely broken with the legacy memcg and direct stalling in |
| * shrink_folio_list() is used for throttling instead, which lacks all the |
| * niceties such as fairness, adaptive pausing, bandwidth proportional |
| * allocation and configurability. |
| * |
| * This function tests whether the vmscan currently in progress can assume |
| * that the normal dirty throttling mechanism is operational. |
| */ |
| static bool writeback_throttling_sane(struct scan_control *sc) |
| { |
| if (!cgroup_reclaim(sc)) |
| return true; |
| #ifdef CONFIG_CGROUP_WRITEBACK |
| if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) |
| return true; |
| #endif |
| return false; |
| } |
| |
| static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg) |
| { |
| if (sc->proactive && sc->proactive_swappiness) |
| return *sc->proactive_swappiness; |
| return mem_cgroup_swappiness(memcg); |
| } |
| #else |
| static bool cgroup_reclaim(struct scan_control *sc) |
| { |
| return false; |
| } |
| |
| static bool root_reclaim(struct scan_control *sc) |
| { |
| return true; |
| } |
| |
| static bool writeback_throttling_sane(struct scan_control *sc) |
| { |
| return true; |
| } |
| |
| static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg) |
| { |
| return READ_ONCE(vm_swappiness); |
| } |
| #endif |
| |
| static void set_task_reclaim_state(struct task_struct *task, |
| struct reclaim_state *rs) |
| { |
| /* Check for an overwrite */ |
| WARN_ON_ONCE(rs && task->reclaim_state); |
| |
| /* Check for the nulling of an already-nulled member */ |
| WARN_ON_ONCE(!rs && !task->reclaim_state); |
| |
| task->reclaim_state = rs; |
| } |
| |
| /* |
| * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to |
| * scan_control->nr_reclaimed. |
| */ |
| static void flush_reclaim_state(struct scan_control *sc) |
| { |
| /* |
| * Currently, reclaim_state->reclaimed includes three types of pages |
| * freed outside of vmscan: |
| * (1) Slab pages. |
| * (2) Clean file pages from pruned inodes (on highmem systems). |
| * (3) XFS freed buffer pages. |
| * |
| * For all of these cases, we cannot universally link the pages to a |
| * single memcg. For example, a memcg-aware shrinker can free one object |
| * charged to the target memcg, causing an entire page to be freed. |
| * If we count the entire page as reclaimed from the memcg, we end up |
| * overestimating the reclaimed amount (potentially under-reclaiming). |
| * |
| * Only count such pages for global reclaim to prevent under-reclaiming |
| * from the target memcg; preventing unnecessary retries during memcg |
| * charging and false positives from proactive reclaim. |
| * |
| * For uncommon cases where the freed pages were actually mostly |
| * charged to the target memcg, we end up underestimating the reclaimed |
| * amount. This should be fine. The freed pages will be uncharged |
| * anyway, even if they are not counted here properly, and we will be |
| * able to make forward progress in charging (which is usually in a |
| * retry loop). |
| * |
| * We can go one step further, and report the uncharged objcg pages in |
| * memcg reclaim, to make reporting more accurate and reduce |
| * underestimation, but it's probably not worth the complexity for now. |
| */ |
| if (current->reclaim_state && root_reclaim(sc)) { |
| sc->nr_reclaimed += current->reclaim_state->reclaimed; |
| current->reclaim_state->reclaimed = 0; |
| } |
| } |
| |
| static bool can_demote(int nid, struct scan_control *sc) |
| { |
| if (!numa_demotion_enabled) |
| return false; |
| if (sc && sc->no_demotion) |
| return false; |
| if (next_demotion_node(nid) == NUMA_NO_NODE) |
| return false; |
| |
| return true; |
| } |
| |
| static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, |
| int nid, |
| struct scan_control *sc) |
| { |
| if (memcg == NULL) { |
| /* |
| * For non-memcg reclaim, is there |
| * space in any swap device? |
| */ |
| if (get_nr_swap_pages() > 0) |
| return true; |
| } else { |
| /* Is the memcg below its swap limit? */ |
| if (mem_cgroup_get_nr_swap_pages(memcg) > 0) |
| return true; |
| } |
| |
| /* |
| * The page can not be swapped. |
| * |
| * Can it be reclaimed from this node via demotion? |
| */ |
| return can_demote(nid, sc); |
| } |
| |
| /* |
| * This misses isolated folios which are not accounted for to save counters. |
| * As the data only determines if reclaim or compaction continues, it is |
| * not expected that isolated folios will be a dominating factor. |
| */ |
| unsigned long zone_reclaimable_pages(struct zone *zone) |
| { |
| unsigned long nr; |
| |
| nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) + |
| zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE); |
| if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL)) |
| nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) + |
| zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON); |
| |
| return nr; |
| } |
| |
| /** |
| * lruvec_lru_size - Returns the number of pages on the given LRU list. |
| * @lruvec: lru vector |
| * @lru: lru to use |
| * @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list) |
| */ |
| static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, |
| int zone_idx) |
| { |
| unsigned long size = 0; |
| int zid; |
| |
| for (zid = 0; zid <= zone_idx; zid++) { |
| struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid]; |
| |
| if (!managed_zone(zone)) |
| continue; |
| |
| if (!mem_cgroup_disabled()) |
| size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid); |
| else |
| size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru); |
| } |
| return size; |
| } |
| |
| static unsigned long drop_slab_node(int nid) |
| { |
| unsigned long freed = 0; |
| struct mem_cgroup *memcg = NULL; |
| |
| memcg = mem_cgroup_iter(NULL, NULL, NULL); |
| do { |
| freed += shrink_slab(GFP_KERNEL, nid, memcg, 0); |
| } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); |
| |
| return freed; |
| } |
| |
| void drop_slab(void) |
| { |
| int nid; |
| int shift = 0; |
| unsigned long freed; |
| |
| do { |
| freed = 0; |
| for_each_online_node(nid) { |
| if (fatal_signal_pending(current)) |
| return; |
| |
| freed += drop_slab_node(nid); |
| } |
| } while ((freed >> shift++) > 1); |
| } |
| |
| static int reclaimer_offset(void) |
| { |
| BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD != |
| PGDEMOTE_DIRECT - PGDEMOTE_KSWAPD); |
| BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD != |
| PGDEMOTE_KHUGEPAGED - PGDEMOTE_KSWAPD); |
| BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD != |
| PGSCAN_DIRECT - PGSCAN_KSWAPD); |
| BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD != |
| PGSCAN_KHUGEPAGED - PGSCAN_KSWAPD); |
| |
| if (current_is_kswapd()) |
| return 0; |
| if (current_is_khugepaged()) |
| return PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD; |
| return PGSTEAL_DIRECT - PGSTEAL_KSWAPD; |
| } |
| |
| static inline int is_page_cache_freeable(struct folio *folio) |
| { |
| /* |
| * A freeable page cache folio is referenced only by the caller |
| * that isolated the folio, the page cache and optional filesystem |
| * private data at folio->private. |
| */ |
| return folio_ref_count(folio) - folio_test_private(folio) == |
| 1 + folio_nr_pages(folio); |
| } |
| |
| /* |
| * We detected a synchronous write error writing a folio out. Probably |
| * -ENOSPC. We need to propagate that into the address_space for a subsequent |
| * fsync(), msync() or close(). |
| * |
| * The tricky part is that after writepage we cannot touch the mapping: nothing |
| * prevents it from being freed up. But we have a ref on the folio and once |
| * that folio is locked, the mapping is pinned. |
| * |
| * We're allowed to run sleeping folio_lock() here because we know the caller has |
| * __GFP_FS. |
| */ |
| static void handle_write_error(struct address_space *mapping, |
| struct folio *folio, int error) |
| { |
| folio_lock(folio); |
| if (folio_mapping(folio) == mapping) |
| mapping_set_error(mapping, error); |
| folio_unlock(folio); |
| } |
| |
| static bool skip_throttle_noprogress(pg_data_t *pgdat) |
| { |
| int reclaimable = 0, write_pending = 0; |
| int i; |
| |
| /* |
| * If kswapd is disabled, reschedule if necessary but do not |
| * throttle as the system is likely near OOM. |
| */ |
| if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES) |
| return true; |
| |
| /* |
| * If there are a lot of dirty/writeback folios then do not |
| * throttle as throttling will occur when the folios cycle |
| * towards the end of the LRU if still under writeback. |
| */ |
| for (i = 0; i < MAX_NR_ZONES; i++) { |
| struct zone *zone = pgdat->node_zones + i; |
| |
| if (!managed_zone(zone)) |
| continue; |
| |
| reclaimable += zone_reclaimable_pages(zone); |
| write_pending += zone_page_state_snapshot(zone, |
| NR_ZONE_WRITE_PENDING); |
| } |
| if (2 * write_pending <= reclaimable) |
| return true; |
| |
| return false; |
| } |
| |
| void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason) |
| { |
| wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason]; |
| long timeout, ret; |
| DEFINE_WAIT(wait); |
| |
| /* |
| * Do not throttle user workers, kthreads other than kswapd or |
| * workqueues. They may be required for reclaim to make |
| * forward progress (e.g. journalling workqueues or kthreads). |
| */ |
| if (!current_is_kswapd() && |
| current->flags & (PF_USER_WORKER|PF_KTHREAD)) { |
| cond_resched(); |
| return; |
| } |
| |
| /* |
| * These figures are pulled out of thin air. |
| * VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many |
| * parallel reclaimers which is a short-lived event so the timeout is |
| * short. Failing to make progress or waiting on writeback are |
| * potentially long-lived events so use a longer timeout. This is shaky |
| * logic as a failure to make progress could be due to anything from |
| * writeback to a slow device to excessive referenced folios at the tail |
| * of the inactive LRU. |
| */ |
| switch(reason) { |
| case VMSCAN_THROTTLE_WRITEBACK: |
| timeout = HZ/10; |
| |
| if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) { |
| WRITE_ONCE(pgdat->nr_reclaim_start, |
| node_page_state(pgdat, NR_THROTTLED_WRITTEN)); |
| } |
| |
| break; |
| case VMSCAN_THROTTLE_CONGESTED: |
| fallthrough; |
| case VMSCAN_THROTTLE_NOPROGRESS: |
| if (skip_throttle_noprogress(pgdat)) { |
| cond_resched(); |
| return; |
| } |
| |
| timeout = 1; |
| |
| break; |
| case VMSCAN_THROTTLE_ISOLATED: |
| timeout = HZ/50; |
| break; |
| default: |
| WARN_ON_ONCE(1); |
| timeout = HZ; |
| break; |
| } |
| |
| prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); |
| ret = schedule_timeout(timeout); |
| finish_wait(wqh, &wait); |
| |
| if (reason == VMSCAN_THROTTLE_WRITEBACK) |
| atomic_dec(&pgdat->nr_writeback_throttled); |
| |
| trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout), |
| jiffies_to_usecs(timeout - ret), |
| reason); |
| } |
| |
| /* |
| * Account for folios written if tasks are throttled waiting on dirty |
| * folios to clean. If enough folios have been cleaned since throttling |
| * started then wakeup the throttled tasks. |
| */ |
| void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio, |
| int nr_throttled) |
| { |
| unsigned long nr_written; |
| |
| node_stat_add_folio(folio, NR_THROTTLED_WRITTEN); |
| |
| /* |
| * This is an inaccurate read as the per-cpu deltas may not |
| * be synchronised. However, given that the system is |
| * writeback throttled, it is not worth taking the penalty |
| * of getting an accurate count. At worst, the throttle |
| * timeout guarantees forward progress. |
| */ |
| nr_written = node_page_state(pgdat, NR_THROTTLED_WRITTEN) - |
| READ_ONCE(pgdat->nr_reclaim_start); |
| |
| if (nr_written > SWAP_CLUSTER_MAX * nr_throttled) |
| wake_up(&pgdat->reclaim_wait[VMSCAN_THROTTLE_WRITEBACK]); |
| } |
| |
| /* possible outcome of pageout() */ |
| typedef enum { |
| /* failed to write folio out, folio is locked */ |
| PAGE_KEEP, |
| /* move folio to the active list, folio is locked */ |
| PAGE_ACTIVATE, |
| /* folio has been sent to the disk successfully, folio is unlocked */ |
| PAGE_SUCCESS, |
| /* folio is clean and locked */ |
| PAGE_CLEAN, |
| } pageout_t; |
| |
| /* |
| * pageout is called by shrink_folio_list() for each dirty folio. |
| * Calls ->writepage(). |
| */ |
| static pageout_t pageout(struct folio *folio, struct address_space *mapping, |
| struct swap_iocb **plug) |
| { |
| /* |
| * If the folio is dirty, only perform writeback if that write |
| * will be non-blocking. To prevent this allocation from being |
| * stalled by pagecache activity. But note that there may be |
| * stalls if we need to run get_block(). We could test |
| * PagePrivate for that. |
| * |
| * If this process is currently in __generic_file_write_iter() against |
| * this folio's queue, we can perform writeback even if that |
| * will block. |
| * |
| * If the folio is swapcache, write it back even if that would |
| * block, for some throttling. This happens by accident, because |
| * swap_backing_dev_info is bust: it doesn't reflect the |
| * congestion state of the swapdevs. Easy to fix, if needed. |
| */ |
| if (!is_page_cache_freeable(folio)) |
| return PAGE_KEEP; |
| if (!mapping) { |
| /* |
| * Some data journaling orphaned folios can have |
| * folio->mapping == NULL while being dirty with clean buffers. |
| */ |
| if (folio_test_private(folio)) { |
| if (try_to_free_buffers(folio)) { |
| folio_clear_dirty(folio); |
| pr_info("%s: orphaned folio\n", __func__); |
| return PAGE_CLEAN; |
| } |
| } |
| return PAGE_KEEP; |
| } |
| if (mapping->a_ops->writepage == NULL) |
| return PAGE_ACTIVATE; |
| |
| if (folio_clear_dirty_for_io(folio)) { |
| int res; |
| struct writeback_control wbc = { |
| .sync_mode = WB_SYNC_NONE, |
| .nr_to_write = SWAP_CLUSTER_MAX, |
| .range_start = 0, |
| .range_end = LLONG_MAX, |
| .for_reclaim = 1, |
| .swap_plug = plug, |
| }; |
| |
| folio_set_reclaim(folio); |
| res = mapping->a_ops->writepage(&folio->page, &wbc); |
| if (res < 0) |
| handle_write_error(mapping, folio, res); |
| if (res == AOP_WRITEPAGE_ACTIVATE) { |
| folio_clear_reclaim(folio); |
| return PAGE_ACTIVATE; |
| } |
| |
| if (!folio_test_writeback(folio)) { |
| /* synchronous write or broken a_ops? */ |
| folio_clear_reclaim(folio); |
| } |
| trace_mm_vmscan_write_folio(folio); |
| node_stat_add_folio(folio, NR_VMSCAN_WRITE); |
| return PAGE_SUCCESS; |
| } |
| |
| return PAGE_CLEAN; |
| } |
| |
| /* |
| * Same as remove_mapping, but if the folio is removed from the mapping, it |
| * gets returned with a refcount of 0. |
| */ |
| static int __remove_mapping(struct address_space *mapping, struct folio *folio, |
| bool reclaimed, struct mem_cgroup *target_memcg) |
| { |
| int refcount; |
| void *shadow = NULL; |
| |
| BUG_ON(!folio_test_locked(folio)); |
| BUG_ON(mapping != folio_mapping(folio)); |
| |
| if (!folio_test_swapcache(folio)) |
| spin_lock(&mapping->host->i_lock); |
| xa_lock_irq(&mapping->i_pages); |
| /* |
| * The non racy check for a busy folio. |
| * |
| * Must be careful with the order of the tests. When someone has |
| * a ref to the folio, it may be possible that they dirty it then |
| * drop the reference. So if the dirty flag is tested before the |
| * refcount here, then the following race may occur: |
| * |
| * get_user_pages(&page); |
| * [user mapping goes away] |
| * write_to(page); |
| * !folio_test_dirty(folio) [good] |
| * folio_set_dirty(folio); |
| * folio_put(folio); |
| * !refcount(folio) [good, discard it] |
| * |
| * [oops, our write_to data is lost] |
| * |
| * Reversing the order of the tests ensures such a situation cannot |
| * escape unnoticed. The smp_rmb is needed to ensure the folio->flags |
| * load is not satisfied before that of folio->_refcount. |
| * |
| * Note that if the dirty flag is always set via folio_mark_dirty, |
| * and thus under the i_pages lock, then this ordering is not required. |
| */ |
| refcount = 1 + folio_nr_pages(folio); |
| if (!folio_ref_freeze(folio, refcount)) |
| goto cannot_free; |
| /* note: atomic_cmpxchg in folio_ref_freeze provides the smp_rmb */ |
| if (unlikely(folio_test_dirty(folio))) { |
| folio_ref_unfreeze(folio, refcount); |
| goto cannot_free; |
| } |
| |
| if (folio_test_swapcache(folio)) { |
| swp_entry_t swap = folio->swap; |
| |
| if (reclaimed && !mapping_exiting(mapping)) |
| shadow = workingset_eviction(folio, target_memcg); |
| __delete_from_swap_cache(folio, swap, shadow); |
| mem_cgroup_swapout(folio, swap); |
| xa_unlock_irq(&mapping->i_pages); |
| put_swap_folio(folio, swap); |
| } else { |
| void (*free_folio)(struct folio *); |
| |
| free_folio = mapping->a_ops->free_folio; |
| /* |
| * Remember a shadow entry for reclaimed file cache in |
| * order to detect refaults, thus thrashing, later on. |
| * |
| * But don't store shadows in an address space that is |
| * already exiting. This is not just an optimization, |
| * inode reclaim needs to empty out the radix tree or |
| * the nodes are lost. Don't plant shadows behind its |
| * back. |
| * |
| * We also don't store shadows for DAX mappings because the |
| * only page cache folios found in these are zero pages |
| * covering holes, and because we don't want to mix DAX |
| * exceptional entries and shadow exceptional entries in the |
| * same address_space. |
| */ |
| if (reclaimed && folio_is_file_lru(folio) && |
| !mapping_exiting(mapping) && !dax_mapping(mapping)) |
| shadow = workingset_eviction(folio, target_memcg); |
| __filemap_remove_folio(folio, shadow); |
| xa_unlock_irq(&mapping->i_pages); |
| if (mapping_shrinkable(mapping)) |
| inode_add_lru(mapping->host); |
| spin_unlock(&mapping->host->i_lock); |
| |
| if (free_folio) |
| free_folio(folio); |
| } |
| |
| return 1; |
| |
| cannot_free: |
| xa_unlock_irq(&mapping->i_pages); |
| if (!folio_test_swapcache(folio)) |
| spin_unlock(&mapping->host->i_lock); |
| return 0; |
| } |
| |
| /** |
| * remove_mapping() - Attempt to remove a folio from its mapping. |
| * @mapping: The address space. |
| * @folio: The folio to remove. |
| * |
| * If the folio is dirty, under writeback or if someone else has a ref |
| * on it, removal will fail. |
| * Return: The number of pages removed from the mapping. 0 if the folio |
| * could not be removed. |
| * Context: The caller should have a single refcount on the folio and |
| * hold its lock. |
| */ |
| long remove_mapping(struct address_space *mapping, struct folio *folio) |
| { |
| if (__remove_mapping(mapping, folio, false, NULL)) { |
| /* |
| * Unfreezing the refcount with 1 effectively |
| * drops the pagecache ref for us without requiring another |
| * atomic operation. |
| */ |
| folio_ref_unfreeze(folio, 1); |
| return folio_nr_pages(folio); |
| } |
| return 0; |
| } |
| |
| /** |
| * folio_putback_lru - Put previously isolated folio onto appropriate LRU list. |
| * @folio: Folio to be returned to an LRU list. |
| * |
| * Add previously isolated @folio to appropriate LRU list. |
| * The folio may still be unevictable for other reasons. |
| * |
| * Context: lru_lock must not be held, interrupts must be enabled. |
| */ |
| void folio_putback_lru(struct folio *folio) |
| { |
| folio_add_lru(folio); |
| folio_put(folio); /* drop ref from isolate */ |
| } |
| |
| enum folio_references { |
| FOLIOREF_RECLAIM, |
| FOLIOREF_RECLAIM_CLEAN, |
| FOLIOREF_KEEP, |
| FOLIOREF_ACTIVATE, |
| }; |
| |
| static enum folio_references folio_check_references(struct folio *folio, |
| struct scan_control *sc) |
| { |
| int referenced_ptes, referenced_folio; |
| unsigned long vm_flags; |
| |
| referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup, |
| &vm_flags); |
| referenced_folio = folio_test_clear_referenced(folio); |
| |
| /* |
| * The supposedly reclaimable folio was found to be in a VM_LOCKED vma. |
| * Let the folio, now marked Mlocked, be moved to the unevictable list. |
| */ |
| if (vm_flags & VM_LOCKED) |
| return FOLIOREF_ACTIVATE; |
| |
| /* rmap lock contention: rotate */ |
| if (referenced_ptes == -1) |
| return FOLIOREF_KEEP; |
| |
| if (referenced_ptes) { |
| /* |
| * All mapped folios start out with page table |
| * references from the instantiating fault, so we need |
| * to look twice if a mapped file/anon folio is used more |
| * than once. |
| * |
| * Mark it and spare it for another trip around the |
| * inactive list. Another page table reference will |
| * lead to its activation. |
| * |
| * Note: the mark is set for activated folios as well |
| * so that recently deactivated but used folios are |
| * quickly recovered. |
| */ |
| folio_set_referenced(folio); |
| |
| if (referenced_folio || referenced_ptes > 1) |
| return FOLIOREF_ACTIVATE; |
| |
| /* |
| * Activate file-backed executable folios after first usage. |
| */ |
| if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) |
| return FOLIOREF_ACTIVATE; |
| |
| return FOLIOREF_KEEP; |
| } |
| |
| /* Reclaim if clean, defer dirty folios to writeback */ |
| if (referenced_folio && folio_is_file_lru(folio)) |
| return FOLIOREF_RECLAIM_CLEAN; |
| |
| return FOLIOREF_RECLAIM; |
| } |
| |
| /* Check if a folio is dirty or under writeback */ |
| static void folio_check_dirty_writeback(struct folio *folio, |
| bool *dirty, bool *writeback) |
| { |
| struct address_space *mapping; |
| |
| /* |
| * Anonymous folios are not handled by flushers and must be written |
| * from reclaim context. Do not stall reclaim based on them. |
| * MADV_FREE anonymous folios are put into inactive file list too. |
| * They could be mistakenly treated as file lru. So further anon |
| * test is needed. |
| */ |
| if (!folio_is_file_lru(folio) || |
| (folio_test_anon(folio) && !folio_test_swapbacked(folio))) { |
| *dirty = false; |
| *writeback = false; |
| return; |
| } |
| |
| /* By default assume that the folio flags are accurate */ |
| *dirty = folio_test_dirty(folio); |
| *writeback = folio_test_writeback(folio); |
| |
| /* Verify dirty/writeback state if the filesystem supports it */ |
| if (!folio_test_private(folio)) |
| return; |
| |
| mapping = folio_mapping(folio); |
| if (mapping && mapping->a_ops->is_dirty_writeback) |
| mapping->a_ops->is_dirty_writeback(folio, dirty, writeback); |
| } |
| |
| struct folio *alloc_migrate_folio(struct folio *src, unsigned long private) |
| { |
| struct folio *dst; |
| nodemask_t *allowed_mask; |
| struct migration_target_control *mtc; |
| |
| mtc = (struct migration_target_control *)private; |
| |
| allowed_mask = mtc->nmask; |
| /* |
| * make sure we allocate from the target node first also trying to |
| * demote or reclaim pages from the target node via kswapd if we are |
| * low on free memory on target node. If we don't do this and if |
| * we have free memory on the slower(lower) memtier, we would start |
| * allocating pages from slower(lower) memory tiers without even forcing |
| * a demotion of cold pages from the target memtier. This can result |
| * in the kernel placing hot pages in slower(lower) memory tiers. |
| */ |
| mtc->nmask = NULL; |
| mtc->gfp_mask |= __GFP_THISNODE; |
| dst = alloc_migration_target(src, (unsigned long)mtc); |
| if (dst) |
| return dst; |
| |
| mtc->gfp_mask &= ~__GFP_THISNODE; |
| mtc->nmask = allowed_mask; |
| |
| return alloc_migration_target(src, (unsigned long)mtc); |
| } |
| |
| /* |
| * Take folios on @demote_folios and attempt to demote them to another node. |
| * Folios which are not demoted are left on @demote_folios. |
| */ |
| static unsigned int demote_folio_list(struct list_head *demote_folios, |
| struct pglist_data *pgdat) |
| { |
| int target_nid = next_demotion_node(pgdat->node_id); |
| unsigned int nr_succeeded; |
| nodemask_t allowed_mask; |
| |
| struct migration_target_control mtc = { |
| /* |
| * Allocate from 'node', or fail quickly and quietly. |
| * When this happens, 'page' will likely just be discarded |
| * instead of migrated. |
| */ |
| .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN | |
| __GFP_NOMEMALLOC | GFP_NOWAIT, |
| .nid = target_nid, |
| .nmask = &allowed_mask, |
| .reason = MR_DEMOTION, |
| }; |
| |
| if (list_empty(demote_folios)) |
| return 0; |
| |
| if (target_nid == NUMA_NO_NODE) |
| return 0; |
| |
| node_get_allowed_targets(pgdat, &allowed_mask); |
| |
| /* Demotion ignores all cpuset and mempolicy settings */ |
| migrate_pages(demote_folios, alloc_migrate_folio, NULL, |
| (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION, |
| &nr_succeeded); |
| |
| mod_node_page_state(pgdat, PGDEMOTE_KSWAPD + reclaimer_offset(), |
| nr_succeeded); |
| |
| return nr_succeeded; |
| } |
| |
| static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask) |
| { |
| if (gfp_mask & __GFP_FS) |
| return true; |
| if (!folio_test_swapcache(folio) || !(gfp_mask & __GFP_IO)) |
| return false; |
| /* |
| * We can "enter_fs" for swap-cache with only __GFP_IO |
| * providing this isn't SWP_FS_OPS. |
| * ->flags can be updated non-atomicially (scan_swap_map_slots), |
| * but that will never affect SWP_FS_OPS, so the data_race |
| * is safe. |
| */ |
| return !data_race(folio_swap_flags(folio) & SWP_FS_OPS); |
| } |
| |
| /* |
| * shrink_folio_list() returns the number of reclaimed pages |
| */ |
| static unsigned int shrink_folio_list(struct list_head *folio_list, |
| struct pglist_data *pgdat, struct scan_control *sc, |
| struct reclaim_stat *stat, bool ignore_references) |
| { |
| struct folio_batch free_folios; |
| LIST_HEAD(ret_folios); |
| LIST_HEAD(demote_folios); |
| unsigned int nr_reclaimed = 0; |
| unsigned int pgactivate = 0; |
| bool do_demote_pass; |
| struct swap_iocb *plug = NULL; |
| |
| folio_batch_init(&free_folios); |
| memset(stat, 0, sizeof(*stat)); |
| cond_resched(); |
| do_demote_pass = can_demote(pgdat->node_id, sc); |
| |
| retry: |
| while (!list_empty(folio_list)) { |
| struct address_space *mapping; |
| struct folio *folio; |
| enum folio_references references = FOLIOREF_RECLAIM; |
| bool dirty, writeback; |
| unsigned int nr_pages; |
| |
| cond_resched(); |
| |
| folio = lru_to_folio(folio_list); |
| list_del(&folio->lru); |
| |
| if (!folio_trylock(folio)) |
| goto keep; |
| |
| VM_BUG_ON_FOLIO(folio_test_active(folio), folio); |
| |
| nr_pages = folio_nr_pages(folio); |
| |
| /* Account the number of base pages */ |
| sc->nr_scanned += nr_pages; |
| |
| if (unlikely(!folio_evictable(folio))) |
| goto activate_locked; |
| |
| if (!sc->may_unmap && folio_mapped(folio)) |
| goto keep_locked; |
| |
| /* folio_update_gen() tried to promote this page? */ |
| if (lru_gen_enabled() && !ignore_references && |
| folio_mapped(folio) && folio_test_referenced(folio)) |
| goto keep_locked; |
| |
| /* |
| * The number of dirty pages determines if a node is marked |
| * reclaim_congested. kswapd will stall and start writing |
| * folios if the tail of the LRU is all dirty unqueued folios. |
| */ |
| folio_check_dirty_writeback(folio, &dirty, &writeback); |
| if (dirty || writeback) |
| stat->nr_dirty += nr_pages; |
| |
| if (dirty && !writeback) |
| stat->nr_unqueued_dirty += nr_pages; |
| |
| /* |
| * Treat this folio as congested if folios are cycling |
| * through the LRU so quickly that the folios marked |
| * for immediate reclaim are making it to the end of |
| * the LRU a second time. |
| */ |
| if (writeback && folio_test_reclaim(folio)) |
| stat->nr_congested += nr_pages; |
| |
| /* |
| * If a folio at the tail of the LRU is under writeback, there |
| * are three cases to consider. |
| * |
| * 1) If reclaim is encountering an excessive number |
| * of folios under writeback and this folio has both |
| * the writeback and reclaim flags set, then it |
| * indicates that folios are being queued for I/O but |
| * are being recycled through the LRU before the I/O |
| * can complete. Waiting on the folio itself risks an |
| * indefinite stall if it is impossible to writeback |
| * the folio due to I/O error or disconnected storage |
| * so instead note that the LRU is being scanned too |
| * quickly and the caller can stall after the folio |
| * list has been processed. |
| * |
| * 2) Global or new memcg reclaim encounters a folio that is |
| * not marked for immediate reclaim, or the caller does not |
| * have __GFP_FS (or __GFP_IO if it's simply going to swap, |
| * not to fs). In this case mark the folio for immediate |
| * reclaim and continue scanning. |
| * |
| * Require may_enter_fs() because we would wait on fs, which |
| * may not have submitted I/O yet. And the loop driver might |
| * enter reclaim, and deadlock if it waits on a folio for |
| * which it is needed to do the write (loop masks off |
| * __GFP_IO|__GFP_FS for this reason); but more thought |
| * would probably show more reasons. |
| * |
| * 3) Legacy memcg encounters a folio that already has the |
| * reclaim flag set. memcg does not have any dirty folio |
| * throttling so we could easily OOM just because too many |
| * folios are in writeback and there is nothing else to |
| * reclaim. Wait for the writeback to complete. |
| * |
| * In cases 1) and 2) we activate the folios to get them out of |
| * the way while we continue scanning for clean folios on the |
| * inactive list and refilling from the active list. The |
| * observation here is that waiting for disk writes is more |
| * expensive than potentially causing reloads down the line. |
| * Since they're marked for immediate reclaim, they won't put |
| * memory pressure on the cache working set any longer than it |
| * takes to write them to disk. |
| */ |
| if (folio_test_writeback(folio)) { |
| /* Case 1 above */ |
| if (current_is_kswapd() && |
| folio_test_reclaim(folio) && |
| test_bit(PGDAT_WRITEBACK, &pgdat->flags)) { |
| stat->nr_immediate += nr_pages; |
| goto activate_locked; |
| |
| /* Case 2 above */ |
| } else if (writeback_throttling_sane(sc) || |
| !folio_test_reclaim(folio) || |
| !may_enter_fs(folio, sc->gfp_mask)) { |
| /* |
| * This is slightly racy - |
| * folio_end_writeback() might have |
| * just cleared the reclaim flag, then |
| * setting the reclaim flag here ends up |
| * interpreted as the readahead flag - but |
| * that does not matter enough to care. |
| * What we do want is for this folio to |
| * have the reclaim flag set next time |
| * memcg reclaim reaches the tests above, |
| * so it will then wait for writeback to |
| * avoid OOM; and it's also appropriate |
| * in global reclaim. |
| */ |
| folio_set_reclaim(folio); |
| stat->nr_writeback += nr_pages; |
| goto activate_locked; |
| |
| /* Case 3 above */ |
| } else { |
| folio_unlock(folio); |
| folio_wait_writeback(folio); |
| /* then go back and try same folio again */ |
| list_add_tail(&folio->lru, folio_list); |
| continue; |
| } |
| } |
| |
| if (!ignore_references) |
| references = folio_check_references(folio, sc); |
| |
| switch (references) { |
| case FOLIOREF_ACTIVATE: |
| goto activate_locked; |
| case FOLIOREF_KEEP: |
| stat->nr_ref_keep += nr_pages; |
| goto keep_locked; |
| case FOLIOREF_RECLAIM: |
| case FOLIOREF_RECLAIM_CLEAN: |
| ; /* try to reclaim the folio below */ |
| } |
| |
| /* |
| * Before reclaiming the folio, try to relocate |
| * its contents to another node. |
| */ |
| if (do_demote_pass && |
| (thp_migration_supported() || !folio_test_large(folio))) { |
| list_add(&folio->lru, &demote_folios); |
| folio_unlock(folio); |
| continue; |
| } |
| |
| /* |
| * Anonymous process memory has backing store? |
| * Try to allocate it some swap space here. |
| * Lazyfree folio could be freed directly |
| */ |
| if (folio_test_anon(folio) && folio_test_swapbacked(folio)) { |
| if (!folio_test_swapcache(folio)) { |
| if (!(sc->gfp_mask & __GFP_IO)) |
| goto keep_locked; |
| if (folio_maybe_dma_pinned(folio)) |
| goto keep_locked; |
| if (folio_test_large(folio)) { |
| /* cannot split folio, skip it */ |
| if (!can_split_folio(folio, NULL)) |
| goto activate_locked; |
| /* |
| * Split partially mapped folios right away. |
| * We can free the unmapped pages without IO. |
| */ |
| if (data_race(!list_empty(&folio->_deferred_list)) && |
| split_folio_to_list(folio, folio_list)) |
| goto activate_locked; |
| } |
| if (!add_to_swap(folio)) { |
| int __maybe_unused order = folio_order(folio); |
| |
| if (!folio_test_large(folio)) |
| goto activate_locked_split; |
| /* Fallback to swap normal pages */ |
| if (split_folio_to_list(folio, folio_list)) |
| goto activate_locked; |
| #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| if (nr_pages >= HPAGE_PMD_NR) { |
| count_memcg_folio_events(folio, |
| THP_SWPOUT_FALLBACK, 1); |
| count_vm_event(THP_SWPOUT_FALLBACK); |
| } |
| count_mthp_stat(order, MTHP_STAT_SWPOUT_FALLBACK); |
| #endif |
| if (!add_to_swap(folio)) |
| goto activate_locked_split; |
| } |
| } |
| } else if (folio_test_swapbacked(folio) && |
| folio_test_large(folio)) { |
| /* Split shmem folio */ |
| if (split_folio_to_list(folio, folio_list)) |
| goto keep_locked; |
| } |
| |
| /* |
| * If the folio was split above, the tail pages will make |
| * their own pass through this function and be accounted |
| * then. |
| */ |
| if ((nr_pages > 1) && !folio_test_large(folio)) { |
| sc->nr_scanned -= (nr_pages - 1); |
| nr_pages = 1; |
| } |
| |
| /* |
| * The folio is mapped into the page tables of one or more |
| * processes. Try to unmap it here. |
| */ |
| if (folio_mapped(folio)) { |
| enum ttu_flags flags = TTU_BATCH_FLUSH; |
| bool was_swapbacked = folio_test_swapbacked(folio); |
| |
| if (folio_test_pmd_mappable(folio)) |
| flags |= TTU_SPLIT_HUGE_PMD; |
| /* |
| * Without TTU_SYNC, try_to_unmap will only begin to |
| * hold PTL from the first present PTE within a large |
| * folio. Some initial PTEs might be skipped due to |
| * races with parallel PTE writes in which PTEs can be |
| * cleared temporarily before being written new present |
| * values. This will lead to a large folio is still |
| * mapped while some subpages have been partially |
| * unmapped after try_to_unmap; TTU_SYNC helps |
| * try_to_unmap acquire PTL from the first PTE, |
| * eliminating the influence of temporary PTE values. |
| */ |
| if (folio_test_large(folio)) |
| flags |= TTU_SYNC; |
| |
| try_to_unmap(folio, flags); |
| if (folio_mapped(folio)) { |
| stat->nr_unmap_fail += nr_pages; |
| if (!was_swapbacked && |
| folio_test_swapbacked(folio)) |
| stat->nr_lazyfree_fail += nr_pages; |
| goto activate_locked; |
| } |
| } |
| |
| /* |
| * Folio is unmapped now so it cannot be newly pinned anymore. |
| * No point in trying to reclaim folio if it is pinned. |
| * Furthermore we don't want to reclaim underlying fs metadata |
| * if the folio is pinned and thus potentially modified by the |
| * pinning process as that may upset the filesystem. |
| */ |
| if (folio_maybe_dma_pinned(folio)) |
| goto activate_locked; |
| |
| mapping = folio_mapping(folio); |
| if (folio_test_dirty(folio)) { |
| /* |
| * Only kswapd can writeback filesystem folios |
| * to avoid risk of stack overflow. But avoid |
| * injecting inefficient single-folio I/O into |
| * flusher writeback as much as possible: only |
| * write folios when we've encountered many |
| * dirty folios, and when we've already scanned |
| * the rest of the LRU for clean folios and see |
| * the same dirty folios again (with the reclaim |
| * flag set). |
| */ |
| if (folio_is_file_lru(folio) && |
| (!current_is_kswapd() || |
| !folio_test_reclaim(folio) || |
| !test_bit(PGDAT_DIRTY, &pgdat->flags))) { |
| /* |
| * Immediately reclaim when written back. |
| * Similar in principle to folio_deactivate() |
| * except we already have the folio isolated |
| * and know it's dirty |
| */ |
| node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE, |
| nr_pages); |
| folio_set_reclaim(folio); |
| |
| goto activate_locked; |
| } |
| |
| if (references == FOLIOREF_RECLAIM_CLEAN) |
| goto keep_locked; |
| if (!may_enter_fs(folio, sc->gfp_mask)) |
| goto keep_locked; |
| if (!sc->may_writepage) |
| goto keep_locked; |
| |
| /* |
| * Folio is dirty. Flush the TLB if a writable entry |
| * potentially exists to avoid CPU writes after I/O |
| * starts and then write it out here. |
| */ |
| try_to_unmap_flush_dirty(); |
| switch (pageout(folio, mapping, &plug)) { |
| case PAGE_KEEP: |
| goto keep_locked; |
| case PAGE_ACTIVATE: |
| goto activate_locked; |
| case PAGE_SUCCESS: |
| stat->nr_pageout += nr_pages; |
| |
| if (folio_test_writeback(folio)) |
| goto keep; |
| if (folio_test_dirty(folio)) |
| goto keep; |
| |
| /* |
| * A synchronous write - probably a ramdisk. Go |
| * ahead and try to reclaim the folio. |
| */ |
| if (!folio_trylock(folio)) |
| goto keep; |
| if (folio_test_dirty(folio) || |
| folio_test_writeback(folio)) |
| goto keep_locked; |
| mapping = folio_mapping(folio); |
| fallthrough; |
| case PAGE_CLEAN: |
| ; /* try to free the folio below */ |
| } |
| } |
| |
| /* |
| * If the folio has buffers, try to free the buffer |
| * mappings associated with this folio. If we succeed |
| * we try to free the folio as well. |
| * |
| * We do this even if the folio is dirty. |
| * filemap_release_folio() does not perform I/O, but it |
| * is possible for a folio to have the dirty flag set, |
| * but it is actually clean (all its buffers are clean). |
| * This happens if the buffers were written out directly, |
| * with submit_bh(). ext3 will do this, as well as |
| * the blockdev mapping. filemap_release_folio() will |
| * discover that cleanness and will drop the buffers |
| * and mark the folio clean - it can be freed. |
| * |
| * Rarely, folios can have buffers and no ->mapping. |
| * These are the folios which were not successfully |
| * invalidated in truncate_cleanup_folio(). We try to |
| * drop those buffers here and if that worked, and the |
| * folio is no longer mapped into process address space |
| * (refcount == 1) it can be freed. Otherwise, leave |
| * the folio on the LRU so it is swappable. |
| */ |
| if (folio_needs_release(folio)) { |
| if (!filemap_release_folio(folio, sc->gfp_mask)) |
| goto activate_locked; |
| if (!mapping && folio_ref_count(folio) == 1) { |
| folio_unlock(folio); |
| if (folio_put_testzero(folio)) |
| goto free_it; |
| else { |
| /* |
| * rare race with speculative reference. |
| * the speculative reference will free |
| * this folio shortly, so we may |
| * increment nr_reclaimed here (and |
| * leave it off the LRU). |
| */ |
| nr_reclaimed += nr_pages; |
| continue; |
| } |
| } |
| } |
| |
| if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) { |
| /* follow __remove_mapping for reference */ |
| if (!folio_ref_freeze(folio, 1)) |
| goto keep_locked; |
| /* |
| * The folio has only one reference left, which is |
| * from the isolation. After the caller puts the |
| * folio back on the lru and drops the reference, the |
| * folio will be freed anyway. It doesn't matter |
| * which lru it goes on. So we don't bother checking |
| * the dirty flag here. |
| */ |
| count_vm_events(PGLAZYFREED, nr_pages); |
| count_memcg_folio_events(folio, PGLAZYFREED, nr_pages); |
| } else if (!mapping || !__remove_mapping(mapping, folio, true, |
| sc->target_mem_cgroup)) |
| goto keep_locked; |
| |
| folio_unlock(folio); |
| free_it: |
| /* |
| * Folio may get swapped out as a whole, need to account |
| * all pages in it. |
| */ |
| nr_reclaimed += nr_pages; |
| |
| folio_undo_large_rmappable(folio); |
| if (folio_batch_add(&free_folios, folio) == 0) { |
| mem_cgroup_uncharge_folios(&free_folios); |
| try_to_unmap_flush(); |
| free_unref_folios(&free_folios); |
| } |
| continue; |
| |
| activate_locked_split: |
| /* |
| * The tail pages that are failed to add into swap cache |
| * reach here. Fixup nr_scanned and nr_pages. |
| */ |
| if (nr_pages > 1) { |
| sc->nr_scanned -= (nr_pages - 1); |
| nr_pages = 1; |
| } |
| activate_locked: |
| /* Not a candidate for swapping, so reclaim swap space. */ |
| if (folio_test_swapcache(folio) && |
| (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio))) |
| folio_free_swap(folio); |
| VM_BUG_ON_FOLIO(folio_test_active(folio), folio); |
| if (!folio_test_mlocked(folio)) { |
| int type = folio_is_file_lru(folio); |
| folio_set_active(folio); |
| stat->nr_activate[type] += nr_pages; |
| count_memcg_folio_events(folio, PGACTIVATE, nr_pages); |
| } |
| keep_locked: |
| folio_unlock(folio); |
| keep: |
| list_add(&folio->lru, &ret_folios); |
| VM_BUG_ON_FOLIO(folio_test_lru(folio) || |
| folio_test_unevictable(folio), folio); |
| } |
| /* 'folio_list' is always empty here */ |
| |
| /* Migrate folios selected for demotion */ |
| nr_reclaimed += demote_folio_list(&demote_folios, pgdat); |
| /* Folios that could not be demoted are still in @demote_folios */ |
| if (!list_empty(&demote_folios)) { |
| /* Folios which weren't demoted go back on @folio_list */ |
| list_splice_init(&demote_folios, folio_list); |
| |
| /* |
| * goto retry to reclaim the undemoted folios in folio_list if |
| * desired. |
| * |
| * Reclaiming directly from top tier nodes is not often desired |
| * due to it breaking the LRU ordering: in general memory |
| * should be reclaimed from lower tier nodes and demoted from |
| * top tier nodes. |
| * |
| * However, disabling reclaim from top tier nodes entirely |
| * would cause ooms in edge scenarios where lower tier memory |
| * is unreclaimable for whatever reason, eg memory being |
| * mlocked or too hot to reclaim. We can disable reclaim |
| * from top tier nodes in proactive reclaim though as that is |
| * not real memory pressure. |
| */ |
| if (!sc->proactive) { |
| do_demote_pass = false; |
| goto retry; |
| } |
| } |
| |
| pgactivate = stat->nr_activate[0] + stat->nr_activate[1]; |
| |
| mem_cgroup_uncharge_folios(&free_folios); |
| try_to_unmap_flush(); |
| free_unref_folios(&free_folios); |
| |
| list_splice(&ret_folios, folio_list); |
| count_vm_events(PGACTIVATE, pgactivate); |
| |
| if (plug) |
| swap_write_unplug(plug); |
| return nr_reclaimed; |
| } |
| |
| unsigned int reclaim_clean_pages_from_list(struct zone *zone, |
| struct list_head *folio_list) |
| { |
| struct scan_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .may_unmap = 1, |
| }; |
| struct reclaim_stat stat; |
| unsigned int nr_reclaimed; |
| struct folio *folio, *next; |
| LIST_HEAD(clean_folios); |
| unsigned int noreclaim_flag; |
| |
| list_for_each_entry_safe(folio, next, folio_list, lru) { |
| if (!folio_test_hugetlb(folio) && folio_is_file_lru(folio) && |
| !folio_test_dirty(folio) && !__folio_test_movable(folio) && |
| !folio_test_unevictable(folio)) { |
| folio_clear_active(folio); |
| list_move(&folio->lru, &clean_folios); |
| } |
| } |
| |
| /* |
| * We should be safe here since we are only dealing with file pages and |
| * we are not kswapd and therefore cannot write dirty file pages. But |
| * call memalloc_noreclaim_save() anyway, just in case these conditions |
| * change in the future. |
| */ |
| noreclaim_flag = memalloc_noreclaim_save(); |
| nr_reclaimed = shrink_folio_list(&clean_folios, zone->zone_pgdat, &sc, |
| &stat, true); |
| memalloc_noreclaim_restore(noreclaim_flag); |
| |
| list_splice(&clean_folios, folio_list); |
| mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, |
| -(long)nr_reclaimed); |
| /* |
| * Since lazyfree pages are isolated from file LRU from the beginning, |
| * they will rotate back to anonymous LRU in the end if it failed to |
| * discard so isolated count will be mismatched. |
| * Compensate the isolated count for both LRU lists. |
| */ |
| mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON, |
| stat.nr_lazyfree_fail); |
| mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, |
| -(long)stat.nr_lazyfree_fail); |
| return nr_reclaimed; |
| } |
| |
| /* |
| * Update LRU sizes after isolating pages. The LRU size updates must |
| * be complete before mem_cgroup_update_lru_size due to a sanity check. |
| */ |
| static __always_inline void update_lru_sizes(struct lruvec *lruvec, |
| enum lru_list lru, unsigned long *nr_zone_taken) |
| { |
| int zid; |
| |
| for (zid = 0; zid < MAX_NR_ZONES; zid++) { |
| if (!nr_zone_taken[zid]) |
| continue; |
| |
| update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]); |
| } |
| |
| } |
| |
| #ifdef CONFIG_CMA |
| /* |
| * It is waste of effort to scan and reclaim CMA pages if it is not available |
| * for current allocation context. Kswapd can not be enrolled as it can not |
| * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL |
| */ |
| static bool skip_cma(struct folio *folio, struct scan_control *sc) |
| { |
| return !current_is_kswapd() && |
| gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE && |
| folio_migratetype(folio) == MIGRATE_CMA; |
| } |
| #else |
| static bool skip_cma(struct folio *folio, struct scan_control *sc) |
| { |
| return false; |
| } |
| #endif |
| |
| /* |
| * Isolating page from the lruvec to fill in @dst list by nr_to_scan times. |
| * |
| * lruvec->lru_lock is heavily contended. Some of the functions that |
| * shrink the lists perform better by taking out a batch of pages |
| * and working on them outside the LRU lock. |
| * |
| * For pagecache intensive workloads, this function is the hottest |
| * spot in the kernel (apart from copy_*_user functions). |
| * |
| * Lru_lock must be held before calling this function. |
| * |
| * @nr_to_scan: The number of eligible pages to look through on the list. |
| * @lruvec: The LRU vector to pull pages from. |
| * @dst: The temp list to put pages on to. |
| * @nr_scanned: The number of pages that were scanned. |
| * @sc: The scan_control struct for this reclaim session |
| * @lru: LRU list id for isolating |
| * |
| * returns how many pages were moved onto *@dst. |
| */ |
| static unsigned long isolate_lru_folios(unsigned long nr_to_scan, |
| struct lruvec *lruvec, struct list_head *dst, |
| unsigned long *nr_scanned, struct scan_control *sc, |
| enum lru_list lru) |
| { |
| struct list_head *src = &lruvec->lists[lru]; |
| unsigned long nr_taken = 0; |
| unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 }; |
| unsigned long nr_skipped[MAX_NR_ZONES] = { 0, }; |
| unsigned long skipped = 0; |
| unsigned long scan, total_scan, nr_pages; |
| LIST_HEAD(folios_skipped); |
| |
| total_scan = 0; |
| scan = 0; |
| while (scan < nr_to_scan && !list_empty(src)) { |
| struct list_head *move_to = src; |
| struct folio *folio; |
| |
| folio = lru_to_folio(src); |
| prefetchw_prev_lru_folio(folio, src, flags); |
| |
| nr_pages = folio_nr_pages(folio); |
| total_scan += nr_pages; |
| |
| if (folio_zonenum(folio) > sc->reclaim_idx || |
| skip_cma(folio, sc)) { |
| nr_skipped[folio_zonenum(folio)] += nr_pages; |
| move_to = &folios_skipped; |
| goto move; |
| } |
| |
| /* |
| * Do not count skipped folios because that makes the function |
| * return with no isolated folios if the LRU mostly contains |
| * ineligible folios. This causes the VM to not reclaim any |
| * folios, triggering a premature OOM. |
| * Account all pages in a folio. |
| */ |
| scan += nr_pages; |
| |
| if (!folio_test_lru(folio)) |
| goto move; |
| if (!sc->may_unmap && folio_mapped(folio)) |
| goto move; |
| |
| /* |
| * Be careful not to clear the lru flag until after we're |
| * sure the folio is not being freed elsewhere -- the |
| * folio release code relies on it. |
| */ |
| if (unlikely(!folio_try_get(folio))) |
| goto move; |
| |
| if (!folio_test_clear_lru(folio)) { |
| /* Another thread is already isolating this folio */ |
| folio_put(folio); |
| goto move; |
| } |
| |
| nr_taken += nr_pages; |
| nr_zone_taken[folio_zonenum(folio)] += nr_pages; |
| move_to = dst; |
| move: |
| list_move(&folio->lru, move_to); |
| } |
| |
| /* |
| * Splice any skipped folios to the start of the LRU list. Note that |
| * this disrupts the LRU order when reclaiming for lower zones but |
| * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX |
| * scanning would soon rescan the same folios to skip and waste lots |
| * of cpu cycles. |
| */ |
| if (!list_empty(&folios_skipped)) { |
| int zid; |
| |
| list_splice(&folios_skipped, src); |
| for (zid = 0; zid < MAX_NR_ZONES; zid++) { |
| if (!nr_skipped[zid]) |
| continue; |
| |
| __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]); |
| skipped += nr_skipped[zid]; |
| } |
| } |
| *nr_scanned = total_scan; |
| trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, |
| total_scan, skipped, nr_taken, lru); |
| update_lru_sizes(lruvec, lru, nr_zone_taken); |
| return nr_taken; |
| } |
| |
| /** |
| * folio_isolate_lru() - Try to isolate a folio from its LRU list. |
| * @folio: Folio to isolate from its LRU list. |
| * |
| * Isolate a @folio from an LRU list and adjust the vmstat statistic |
| * corresponding to whatever LRU list the folio was on. |
| * |
| * The folio will have its LRU flag cleared. If it was found on the |
| * active list, it will have the Active flag set. If it was found on the |
| * unevictable list, it will have the Unevictable flag set. These flags |
| * may need to be cleared by the caller before letting the page go. |
| * |
| * Context: |
| * |
| * (1) Must be called with an elevated refcount on the folio. This is a |
| * fundamental difference from isolate_lru_folios() (which is called |
| * without a stable reference). |
| * (2) The lru_lock must not be held. |
| * (3) Interrupts must be enabled. |
| * |
| * Return: true if the folio was removed from an LRU list. |
| * false if the folio was not on an LRU list. |
| */ |
| bool folio_isolate_lru(struct folio *folio) |
| { |
| bool ret = false; |
| |
| VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio); |
| |
| if (folio_test_clear_lru(folio)) { |
| struct lruvec *lruvec; |
| |
| folio_get(folio); |
| lruvec = folio_lruvec_lock_irq(folio); |
| lruvec_del_folio(lruvec, folio); |
| unlock_page_lruvec_irq(lruvec); |
| ret = true; |
| } |
| |
| return ret; |
| } |
| |
| /* |
| * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and |
| * then get rescheduled. When there are massive number of tasks doing page |
| * allocation, such sleeping direct reclaimers may keep piling up on each CPU, |
| * the LRU list will go small and be scanned faster than necessary, leading to |
| * unnecessary swapping, thrashing and OOM. |
| */ |
| static bool too_many_isolated(struct pglist_data *pgdat, int file, |
| struct scan_control *sc) |
| { |
| unsigned long inactive, isolated; |
| bool too_many; |
| |
| if (current_is_kswapd()) |
| return false; |
| |
| if (!writeback_throttling_sane(sc)) |
| return false; |
| |
| if (file) { |
| inactive = node_page_state(pgdat, NR_INACTIVE_FILE); |
| isolated = node_page_state(pgdat, NR_ISOLATED_FILE); |
| } else { |
| inactive = node_page_state(pgdat, NR_INACTIVE_ANON); |
| isolated = node_page_state(pgdat, NR_ISOLATED_ANON); |
| } |
| |
| /* |
| * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they |
| * won't get blocked by normal direct-reclaimers, forming a circular |
| * deadlock. |
| */ |
| if (gfp_has_io_fs(sc->gfp_mask)) |
| inactive >>= 3; |
| |
| too_many = isolated > inactive; |
| |
| /* Wake up tasks throttled due to too_many_isolated. */ |
| if (!too_many) |
| wake_throttle_isolated(pgdat); |
| |
| return too_many; |
| } |
| |
| /* |
| * move_folios_to_lru() moves folios from private @list to appropriate LRU list. |
| * |
| * Returns the number of pages moved to the given lruvec. |
| */ |
| static unsigned int move_folios_to_lru(struct lruvec *lruvec, |
| struct list_head *list) |
| { |
| int nr_pages, nr_moved = 0; |
| struct folio_batch free_folios; |
| |
| folio_batch_init(&free_folios); |
| while (!list_empty(list)) { |
| struct folio *folio = lru_to_folio(list); |
| |
| VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); |
| list_del(&folio->lru); |
| if (unlikely(!folio_evictable(folio))) { |
| spin_unlock_irq(&lruvec->lru_lock); |
| folio_putback_lru(folio); |
| spin_lock_irq(&lruvec->lru_lock); |
| continue; |
| } |
| |
| /* |
| * The folio_set_lru needs to be kept here for list integrity. |
| * Otherwise: |
| * #0 move_folios_to_lru #1 release_pages |
| * if (!folio_put_testzero()) |
| * if (folio_put_testzero()) |
| * !lru //skip lru_lock |
| * folio_set_lru() |
| * list_add(&folio->lru,) |
| * list_add(&folio->lru,) |
| */ |
| folio_set_lru(folio); |
| |
| if (unlikely(folio_put_testzero(folio))) { |
| __folio_clear_lru_flags(folio); |
| |
| folio_undo_large_rmappable(folio); |
| if (folio_batch_add(&free_folios, folio) == 0) { |
| spin_unlock_irq(&lruvec->lru_lock); |
| mem_cgroup_uncharge_folios(&free_folios); |
| free_unref_folios(&free_folios); |
| spin_lock_irq(&lruvec->lru_lock); |
| } |
| |
| continue; |
| } |
| |
| /* |
| * All pages were isolated from the same lruvec (and isolation |
| * inhibits memcg migration). |
| */ |
| VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio, lruvec), folio); |
| lruvec_add_folio(lruvec, folio); |
| nr_pages = folio_nr_pages(folio); |
| nr_moved += nr_pages; |
| if (folio_test_active(folio)) |
| workingset_age_nonresident(lruvec, nr_pages); |
| } |
| |
| if (free_folios.nr) { |
| spin_unlock_irq(&lruvec->lru_lock); |
| mem_cgroup_uncharge_folios(&free_folios); |
| free_unref_folios(&free_folios); |
| spin_lock_irq(&lruvec->lru_lock); |
| } |
| |
| return nr_moved; |
| } |
| |
| /* |
| * If a kernel thread (such as nfsd for loop-back mounts) services a backing |
| * device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case |
| * we should not throttle. Otherwise it is safe to do so. |
| */ |
| static int current_may_throttle(void) |
| { |
| return !(current->flags & PF_LOCAL_THROTTLE); |
| } |
| |
| /* |
| * shrink_inactive_list() is a helper for shrink_node(). It returns the number |
| * of reclaimed pages |
| */ |
| static unsigned long shrink_inactive_list(unsigned long nr_to_scan, |
| struct lruvec *lruvec, struct scan_control *sc, |
| enum lru_list lru) |
| { |
| LIST_HEAD(folio_list); |
| unsigned long nr_scanned; |
| unsigned int nr_reclaimed = 0; |
| unsigned long nr_taken; |
| struct reclaim_stat stat; |
| bool file = is_file_lru(lru); |
| enum vm_event_item item; |
| struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| bool stalled = false; |
| |
| while (unlikely(too_many_isolated(pgdat, file, sc))) { |
| if (stalled) |
| return 0; |
| |
| /* wait a bit for the reclaimer. */ |
| stalled = true; |
| reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED); |
| |
| /* We are about to die and free our memory. Return now. */ |
| if (fatal_signal_pending(current)) |
| return SWAP_CLUSTER_MAX; |
| } |
| |
| lru_add_drain(); |
| |
| spin_lock_irq(&lruvec->lru_lock); |
| |
| nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &folio_list, |
| &nr_scanned, sc, lru); |
| |
| __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken); |
| item = PGSCAN_KSWAPD + reclaimer_offset(); |
| if (!cgroup_reclaim(sc)) |
| __count_vm_events(item, nr_scanned); |
| __count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned); |
| __count_vm_events(PGSCAN_ANON + file, nr_scanned); |
| |
| spin_unlock_irq(&lruvec->lru_lock); |
| |
| if (nr_taken == 0) |
| return 0; |
| |
| nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false); |
| |
| spin_lock_irq(&lruvec->lru_lock); |
| move_folios_to_lru(lruvec, &folio_list); |
| |
| __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); |
| item = PGSTEAL_KSWAPD + reclaimer_offset(); |
| if (!cgroup_reclaim(sc)) |
| __count_vm_events(item, nr_reclaimed); |
| __count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed); |
| __count_vm_events(PGSTEAL_ANON + file, nr_reclaimed); |
| spin_unlock_irq(&lruvec->lru_lock); |
| |
| lru_note_cost(lruvec, file, stat.nr_pageout, nr_scanned - nr_reclaimed); |
| |
| /* |
| * If dirty folios are scanned that are not queued for IO, it |
| * implies that flushers are not doing their job. This can |
| * happen when memory pressure pushes dirty folios to the end of |
| * the LRU before the dirty limits are breached and the dirty |
| * data has expired. It can also happen when the proportion of |
| * dirty folios grows not through writes but through memory |
| * pressure reclaiming all the clean cache. And in some cases, |
| * the flushers simply cannot keep up with the allocation |
| * rate. Nudge the flusher threads in case they are asleep. |
| */ |
| if (stat.nr_unqueued_dirty == nr_taken) { |
| wakeup_flusher_threads(WB_REASON_VMSCAN); |
| /* |
| * For cgroupv1 dirty throttling is achieved by waking up |
| * the kernel flusher here and later waiting on folios |
| * which are in writeback to finish (see shrink_folio_list()). |
| * |
| * Flusher may not be able to issue writeback quickly |
| * enough for cgroupv1 writeback throttling to work |
| * on a large system. |
| */ |
| if (!writeback_throttling_sane(sc)) |
| reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK); |
| } |
| |
| sc->nr.dirty += stat.nr_dirty; |
| sc->nr.congested += stat.nr_congested; |
| sc->nr.unqueued_dirty += stat.nr_unqueued_dirty; |
| sc->nr.writeback += stat.nr_writeback; |
| sc->nr.immediate += stat.nr_immediate; |
| sc->nr.taken += nr_taken; |
| if (file) |
| sc->nr.file_taken += nr_taken; |
| |
| trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id, |
| nr_scanned, nr_reclaimed, &stat, sc->priority, file); |
| return nr_reclaimed; |
| } |
| |
| /* |
| * shrink_active_list() moves folios from the active LRU to the inactive LRU. |
| * |
| * We move them the other way if the folio is referenced by one or more |
| * processes. |
| * |
| * If the folios are mostly unmapped, the processing is fast and it is |
| * appropriate to hold lru_lock across the whole operation. But if |
| * the folios are mapped, the processing is slow (folio_referenced()), so |
| * we should drop lru_lock around each folio. It's impossible to balance |
| * this, so instead we remove the folios from the LRU while processing them. |
| * It is safe to rely on the active flag against the non-LRU folios in here |
| * because nobody will play with that bit on a non-LRU folio. |
| * |
| * The downside is that we have to touch folio->_refcount against each folio. |
| * But we had to alter folio->flags anyway. |
| */ |
| static void shrink_active_list(unsigned long nr_to_scan, |
| struct lruvec *lruvec, |
| struct scan_control *sc, |
| enum lru_list lru) |
| { |
| unsigned long nr_taken; |
| unsigned long nr_scanned; |
| unsigned long vm_flags; |
| LIST_HEAD(l_hold); /* The folios which were snipped off */ |
| LIST_HEAD(l_active); |
| LIST_HEAD(l_inactive); |
| unsigned nr_deactivate, nr_activate; |
| unsigned nr_rotated = 0; |
| bool file = is_file_lru(lru); |
| struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| |
| lru_add_drain(); |
| |
| spin_lock_irq(&lruvec->lru_lock); |
| |
| nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &l_hold, |
| &nr_scanned, sc, lru); |
| |
| __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken); |
| |
| if (!cgroup_reclaim(sc)) |
| __count_vm_events(PGREFILL, nr_scanned); |
| __count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned); |
| |
| spin_unlock_irq(&lruvec->lru_lock); |
| |
| while (!list_empty(&l_hold)) { |
| struct folio *folio; |
| |
| cond_resched(); |
| folio = lru_to_folio(&l_hold); |
| list_del(&folio->lru); |
| |
| if (unlikely(!folio_evictable(folio))) { |
| folio_putback_lru(folio); |
| continue; |
| } |
| |
| if (unlikely(buffer_heads_over_limit)) { |
| if (folio_needs_release(folio) && |
| folio_trylock(folio)) { |
| filemap_release_folio(folio, 0); |
| folio_unlock(folio); |
| } |
| } |
| |
| /* Referenced or rmap lock contention: rotate */ |
| if (folio_referenced(folio, 0, sc->target_mem_cgroup, |
| &vm_flags) != 0) { |
| /* |
| * Identify referenced, file-backed active folios and |
| * give them one more trip around the active list. So |
| * that executable code get better chances to stay in |
| * memory under moderate memory pressure. Anon folios |
| * are not likely to be evicted by use-once streaming |
| * IO, plus JVM can create lots of anon VM_EXEC folios, |
| * so we ignore them here. |
| */ |
| if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) { |
| nr_rotated += folio_nr_pages(folio); |
| list_add(&folio->lru, &l_active); |
| continue; |
| } |
| } |
| |
| folio_clear_active(folio); /* we are de-activating */ |
| folio_set_workingset(folio); |
| list_add(&folio->lru, &l_inactive); |
| } |
| |
| /* |
| * Move folios back to the lru list. |
| */ |
| spin_lock_irq(&lruvec->lru_lock); |
| |
| nr_activate = move_folios_to_lru(lruvec, &l_active); |
| nr_deactivate = move_folios_to_lru(lruvec, &l_inactive); |
| |
| __count_vm_events(PGDEACTIVATE, nr_deactivate); |
| __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate); |
| |
| __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); |
| spin_unlock_irq(&lruvec->lru_lock); |
| |
| if (nr_rotated) |
| lru_note_cost(lruvec, file, 0, nr_rotated); |
| trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate, |
| nr_deactivate, nr_rotated, sc->priority, file); |
| } |
| |
| static unsigned int reclaim_folio_list(struct list_head *folio_list, |
| struct pglist_data *pgdat) |
| { |
| struct reclaim_stat dummy_stat; |
| unsigned int nr_reclaimed; |
| struct folio *folio; |
| struct scan_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .may_writepage = 1, |
| .may_unmap = 1, |
| .may_swap = 1, |
| .no_demotion = 1, |
| }; |
| |
| nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, true); |
| while (!list_empty(folio_list)) { |
| folio = lru_to_folio(folio_list); |
| list_del(&folio->lru); |
| folio_putback_lru(folio); |
| } |
| |
| return nr_reclaimed; |
| } |
| |
| unsigned long reclaim_pages(struct list_head *folio_list) |
| { |
| int nid; |
| unsigned int nr_reclaimed = 0; |
| LIST_HEAD(node_folio_list); |
| unsigned int noreclaim_flag; |
| |
| if (list_empty(folio_list)) |
| return nr_reclaimed; |
| |
| noreclaim_flag = memalloc_noreclaim_save(); |
| |
| nid = folio_nid(lru_to_folio(folio_list)); |
| do { |
| struct folio *folio = lru_to_folio(folio_list); |
| |
| if (nid == folio_nid(folio)) { |
| folio_clear_active(folio); |
| list_move(&folio->lru, &node_folio_list); |
| continue; |
| } |
| |
| nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid)); |
| nid = folio_nid(lru_to_folio(folio_list)); |
| } while (!list_empty(folio_list)); |
| |
| nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid)); |
| |
| memalloc_noreclaim_restore(noreclaim_flag); |
| |
| return nr_reclaimed; |
| } |
| |
| static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
| struct lruvec *lruvec, struct scan_control *sc) |
| { |
| if (is_active_lru(lru)) { |
| if (sc->may_deactivate & (1 << is_file_lru(lru))) |
| shrink_active_list(nr_to_scan, lruvec, sc, lru); |
| else |
| sc->skipped_deactivate = 1; |
| return 0; |
| } |
| |
| return shrink_inactive_list(nr_to_scan, lruvec, sc, lru); |
| } |
| |
| /* |
| * The inactive anon list should be small enough that the VM never has |
| * to do too much work. |
| * |
| * The inactive file list should be small enough to leave most memory |
| * to the established workingset on the scan-resistant active list, |
| * but large enough to avoid thrashing the aggregate readahead window. |
| * |
| * Both inactive lists should also be large enough that each inactive |
| * folio has a chance to be referenced again before it is reclaimed. |
| * |
| * If that fails and refaulting is observed, the inactive list grows. |
| * |
| * The inactive_ratio is the target ratio of ACTIVE to INACTIVE folios |
| * on this LRU, maintained by the pageout code. An inactive_ratio |
| * of 3 means 3:1 or 25% of the folios are kept on the inactive list. |
| * |
| * total target max |
| * memory ratio inactive |
| * ------------------------------------- |
| * 10MB 1 5MB |
| * 100MB 1 50MB |
| * 1GB 3 250MB |
| * 10GB 10 0.9GB |
| * 100GB 31 3GB |
| * 1TB 101 10GB |
| * 10TB 320 32GB |
| */ |
| static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru) |
| { |
| enum lru_list active_lru = inactive_lru + LRU_ACTIVE; |
| unsigned long inactive, active; |
| unsigned long inactive_ratio; |
| unsigned long gb; |
| |
| inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru); |
| active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru); |
| |
| gb = (inactive + active) >> (30 - PAGE_SHIFT); |
| if (gb) |
| inactive_ratio = int_sqrt(10 * gb); |
| else |
| inactive_ratio = 1; |
| |
| return inactive * inactive_ratio < active; |
| } |
| |
| enum scan_balance { |
| SCAN_EQUAL, |
| SCAN_FRACT, |
| SCAN_ANON, |
| SCAN_FILE, |
| }; |
| |
| static void prepare_scan_control(pg_data_t *pgdat, struct scan_control *sc) |
| { |
| unsigned long file; |
| struct lruvec *target_lruvec; |
| |
| if (lru_gen_enabled()) |
| return; |
| |
| target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); |
| |
| /* |
| * Flush the memory cgroup stats, so that we read accurate per-memcg |
| * lruvec stats for heuristics. |
| */ |
| mem_cgroup_flush_stats(sc->target_mem_cgroup); |
| |
| /* |
| * Determine the scan balance between anon and file LRUs. |
| */ |
| spin_lock_irq(&target_lruvec->lru_lock); |
| sc->anon_cost = target_lruvec->anon_cost; |
| sc->file_cost = target_lruvec->file_cost; |
| spin_unlock_irq(&target_lruvec->lru_lock); |
| |
| /* |
| * Target desirable inactive:active list ratios for the anon |
| * and file LRU lists. |
| */ |
| if (!sc->force_deactivate) { |
| unsigned long refaults; |
| |
| /* |
| * When refaults are being observed, it means a new |
| * workingset is being established. Deactivate to get |
| * rid of any stale active pages quickly. |
| */ |
| refaults = lruvec_page_state(target_lruvec, |
| WORKINGSET_ACTIVATE_ANON); |
| if (refaults != target_lruvec->refaults[WORKINGSET_ANON] || |
| inactive_is_low(target_lruvec, LRU_INACTIVE_ANON)) |
| sc->may_deactivate |= DEACTIVATE_ANON; |
| else |
| sc->may_deactivate &= ~DEACTIVATE_ANON; |
| |
| refaults = lruvec_page_state(target_lruvec, |
| WORKINGSET_ACTIVATE_FILE); |
| if (refaults != target_lruvec->refaults[WORKINGSET_FILE] || |
| inactive_is_low(target_lruvec, LRU_INACTIVE_FILE)) |
| sc->may_deactivate |= DEACTIVATE_FILE; |
| else |
| sc->may_deactivate &= ~DEACTIVATE_FILE; |
| } else |
| sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE; |
| |
| /* |
| * If we have plenty of inactive file pages that aren't |
| * thrashing, try to reclaim those first before touching |
| * anonymous pages. |
| */ |
| file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE); |
| if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE) && |
| !sc->no_cache_trim_mode) |
| sc->cache_trim_mode = 1; |
| else |
| sc->cache_trim_mode = 0; |
| |
| /* |
| * Prevent the reclaimer from falling into the cache trap: as |
| * cache pages start out inactive, every cache fault will tip |
| * the scan balance towards the file LRU. And as the file LRU |
| * shrinks, so does the window for rotation from references. |
| * This means we have a runaway feedback loop where a tiny |
| * thrashing file LRU becomes infinitely more attractive than |
| * anon pages. Try to detect this based on file LRU size. |
| */ |
| if (!cgroup_reclaim(sc)) { |
| unsigned long total_high_wmark = 0; |
| unsigned long free, anon; |
| int z; |
| |
| free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES); |
| file = node_page_state(pgdat, NR_ACTIVE_FILE) + |
| node_page_state(pgdat, NR_INACTIVE_FILE); |
| |
| for (z = 0; z < MAX_NR_ZONES; z++) { |
| struct zone *zone = &pgdat->node_zones[z]; |
| |
| if (!managed_zone(zone)) |
| continue; |
| |
| total_high_wmark += high_wmark_pages(zone); |
| } |
| |
| /* |
| * Consider anon: if that's low too, this isn't a |
| * runaway file reclaim problem, but rather just |
| * extreme pressure. Reclaim as per usual then. |
| */ |
| anon = node_page_state(pgdat, NR_INACTIVE_ANON); |
| |
| sc->file_is_tiny = |
| file + free <= total_high_wmark && |
| !(sc->may_deactivate & DEACTIVATE_ANON) && |
| anon >> sc->priority; |
| } |
| } |
| |
| /* |
| * Determine how aggressively the anon and file LRU lists should be |
| * scanned. |
| * |
| * nr[0] = anon inactive folios to scan; nr[1] = anon active folios to scan |
| * nr[2] = file inactive folios to scan; nr[3] = file active folios to scan |
| */ |
| static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, |
| unsigned long *nr) |
| { |
| struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| struct mem_cgroup *memcg = lruvec_memcg(lruvec); |
| unsigned long anon_cost, file_cost, total_cost; |
| int swappiness = sc_swappiness(sc, memcg); |
| u64 fraction[ANON_AND_FILE]; |
| u64 denominator = 0; /* gcc */ |
| enum scan_balance scan_balance; |
| unsigned long ap, fp; |
| enum lru_list lru; |
| |
| /* If we have no swap space, do not bother scanning anon folios. */ |
| if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) { |
| scan_balance = SCAN_FILE; |
| goto out; |
| } |
| |
| /* |
| * Global reclaim will swap to prevent OOM even with no |
| * swappiness, but memcg users want to use this knob to |
| * disable swapping for individual groups completely when |
| * using the memory controller's swap limit feature would be |
| * too expensive. |
| */ |
| if (cgroup_reclaim(sc) && !swappiness) { |
| scan_balance = SCAN_FILE; |
| goto out; |
| } |
| |
| /* |
| * Do not apply any pressure balancing cleverness when the |
| * system is close to OOM, scan both anon and file equally |
| * (unless the swappiness setting disagrees with swapping). |
| */ |
| if (!sc->priority && swappiness) { |
| scan_balance = SCAN_EQUAL; |
| goto out; |
| } |
| |
| /* |
| * If the system is almost out of file pages, force-scan anon. |
| */ |
| if (sc->file_is_tiny) { |
| scan_balance = SCAN_ANON; |
| goto out; |
| } |
| |
| /* |
| * If there is enough inactive page cache, we do not reclaim |
| * anything from the anonymous working right now. |
| */ |
| if (sc->cache_trim_mode) { |
| scan_balance = SCAN_FILE; |
| goto out; |
| } |
| |
| scan_balance = SCAN_FRACT; |
| /* |
| * Calculate the pressure balance between anon and file pages. |
| * |
| * The amount of pressure we put on each LRU is inversely |
| * proportional to the cost of reclaiming each list, as |
| * determined by the share of pages that are refaulting, times |
| * the relative IO cost of bringing back a swapped out |
| * anonymous page vs reloading a filesystem page (swappiness). |
| * |
| * Although we limit that influence to ensure no list gets |
| * left behind completely: at least a third of the pressure is |
| * applied, before swappiness. |
| * |
| * With swappiness at 100, anon and file have equal IO cost. |
| */ |
| total_cost = sc->anon_cost + sc->file_cost; |
| anon_cost = total_cost + sc->anon_cost; |
| file_cost = total_cost + sc->file_cost; |
| total_cost = anon_cost + file_cost; |
| |
| ap = swappiness * (total_cost + 1); |
| ap /= anon_cost + 1; |
| |
| fp = (MAX_SWAPPINESS - swappiness) * (total_cost + 1); |
| fp /= file_cost + 1; |
| |
| fraction[0] = ap; |
| fraction[1] = fp; |
| denominator = ap + fp; |
| out: |
| for_each_evictable_lru(lru) { |
| bool file = is_file_lru(lru); |
| unsigned long lruvec_size; |
| unsigned long low, min; |
| unsigned long scan; |
| |
| lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); |
| mem_cgroup_protection(sc->target_mem_cgroup, memcg, |
| &min, &low); |
| |
| if (min || low) { |
| /* |
| * Scale a cgroup's reclaim pressure by proportioning |
| * its current usage to its memory.low or memory.min |
| * setting. |
| * |
| * This is important, as otherwise scanning aggression |
| * becomes extremely binary -- from nothing as we |
| * approach the memory protection threshold, to totally |
| * nominal as we exceed it. This results in requiring |
| * setting extremely liberal protection thresholds. It |
| * also means we simply get no protection at all if we |
| * set it too low, which is not ideal. |
| * |
| * If there is any protection in place, we reduce scan |
| * pressure by how much of the total memory used is |
| * within protection thresholds. |
| * |
| * There is one special case: in the first reclaim pass, |
| * we skip over all groups that are within their low |
| * protection. If that fails to reclaim enough pages to |
| * satisfy the reclaim goal, we come back and override |
| * the best-effort low protection. However, we still |
| * ideally want to honor how well-behaved groups are in |
| * that case instead of simply punishing them all |
| * equally. As such, we reclaim them based on how much |
| * memory they are using, reducing the scan pressure |
| * again by how much of the total memory used is under |
| * hard protection. |
| */ |
| unsigned long cgroup_size = mem_cgroup_size(memcg); |
| unsigned long protection; |
| |
| /* memory.low scaling, make sure we retry before OOM */ |
| if (!sc->memcg_low_reclaim && low > min) { |
| protection = low; |
| sc->memcg_low_skipped = 1; |
| } else { |
| protection = min; |
| } |
| |
| /* Avoid TOCTOU with earlier protection check */ |
| cgroup_size = max(cgroup_size, protection); |
| |
| scan = lruvec_size - lruvec_size * protection / |
| (cgroup_size + 1); |
| |
| /* |
| * Minimally target SWAP_CLUSTER_MAX pages to keep |
| * reclaim moving forwards, avoiding decrementing |
| * sc->priority further than desirable. |
| */ |
| scan = max(scan, SWAP_CLUSTER_MAX); |
| } else { |
| scan = lruvec_size; |
| } |
| |
| scan >>= sc->priority; |
| |
| /* |
| * If the cgroup's already been deleted, make sure to |
| * scrape out the remaining cache. |
| */ |
| if (!scan && !mem_cgroup_online(memcg)) |
| scan = min(lruvec_size, SWAP_CLUSTER_MAX); |
| |
| switch (scan_balance) { |
| case SCAN_EQUAL: |
| /* Scan lists relative to size */ |
| break; |
| case SCAN_FRACT: |
| /* |
| * Scan types proportional to swappiness and |
| * their relative recent reclaim efficiency. |
| * Make sure we don't miss the last page on |
| * the offlined memory cgroups because of a |
| * round-off error. |
| */ |
| scan = mem_cgroup_online(memcg) ? |
| div64_u64(scan * fraction[file], denominator) : |
| DIV64_U64_ROUND_UP(scan * fraction[file], |
| denominator); |
| break; |
| case SCAN_FILE: |
| case SCAN_ANON: |
| /* Scan one type exclusively */ |
| if ((scan_balance == SCAN_FILE) != file) |
| scan = 0; |
| break; |
| default: |
| /* Look ma, no brain */ |
| BUG(); |
| } |
| |
| nr[lru] = scan; |
| } |
| } |
| |
| /* |
| * Anonymous LRU management is a waste if there is |
| * ultimately no way to reclaim the memory. |
| */ |
| static bool can_age_anon_pages(struct pglist_data *pgdat, |
| struct scan_control *sc) |
| { |
| /* Aging the anon LRU is valuable if swap is present: */ |
| if (total_swap_pages > 0) |
| return true; |
| |
| /* Also valuable if anon pages can be demoted: */ |
| return can_demote(pgdat->node_id, sc); |
| } |
| |
| #ifdef CONFIG_LRU_GEN |
| |
| #ifdef CONFIG_LRU_GEN_ENABLED |
| DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS); |
| #define get_cap(cap) static_branch_likely(&lru_gen_caps[cap]) |
| #else |
| DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS); |
| #define get_cap(cap) static_branch_unlikely(&lru_gen_caps[cap]) |
| #endif |
| |
| static bool should_walk_mmu(void) |
| { |
| return arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK); |
| } |
| |
| static bool should_clear_pmd_young(void) |
| { |
| return arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG); |
| } |
| |
| /****************************************************************************** |
| * shorthand helpers |
| ******************************************************************************/ |
| |
| #define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset)) |
| |
| #define DEFINE_MAX_SEQ(lruvec) \ |
| unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq) |
| |
| #define DEFINE_MIN_SEQ(lruvec) \ |
| unsigned long min_seq[ANON_AND_FILE] = { \ |
| READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]), \ |
| READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]), \ |
| } |
| |
| #define for_each_gen_type_zone(gen, type, zone) \ |
| for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++) \ |
| for ((type) = 0; (type) < ANON_AND_FILE; (type)++) \ |
| for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++) |
| |
| #define get_memcg_gen(seq) ((seq) % MEMCG_NR_GENS) |
| #define get_memcg_bin(bin) ((bin) % MEMCG_NR_BINS) |
| |
| static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid) |
| { |
| struct pglist_data *pgdat = NODE_DATA(nid); |
| |
| #ifdef CONFIG_MEMCG |
| if (memcg) { |
| struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec; |
| |
| /* see the comment in mem_cgroup_lruvec() */ |
| if (!lruvec->pgdat) |
| lruvec->pgdat = pgdat; |
| |
| return lruvec; |
| } |
| #endif |
| VM_WARN_ON_ONCE(!mem_cgroup_disabled()); |
| |
| return &pgdat->__lruvec; |
| } |
| |
| static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc) |
| { |
| struct mem_cgroup *memcg = lruvec_memcg(lruvec); |
| struct pglist_data *pgdat = lruvec_pgdat(lruvec); |
| |
| if (!sc->may_swap) |
| return 0; |
| |
| if (!can_demote(pgdat->node_id, sc) && |
| mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH) |
| return 0; |
| |
| return sc_swappiness(sc, memcg); |
| } |
| |
| static int get_nr_gens(struct lruvec *lruvec, int type) |
| { |
| return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1; |
| } |
| |
| static bool __maybe_unused seq_is_valid(struct lruvec *lruvec) |
| { |
| /* see the comment on lru_gen_folio */ |
| return get_nr_gens(lruvec, LRU_GEN_FILE) >= MIN_NR_GENS && |
| get_nr_gens(lruvec, LRU_GEN_FILE) <= get_nr_gens(lruvec, LRU_GEN_ANON) && |
| get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS; |
| } |
| |
| /****************************************************************************** |
| * Bloom filters |
| ******************************************************************************/ |
| |
| /* |
| * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when |
| * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of |
| * bits in a bitmap, k is the number of hash functions and n is the number of |
| * inserted items. |
| * |
| * Page table walkers use one of the two filters to reduce their search space. |
| * To get rid of non-leaf entries that no longer have enough leaf entries, the |
| * aging uses the double-buffering technique to flip to the other filter each |
| * time it produces a new generation. For non-leaf entries that have enough |
| * leaf entries, the aging carries them over to the next generation in |
| * walk_pmd_range(); the eviction also report them when walking the rmap |
| * in lru_gen_look_around(). |
| * |
| * For future optimizations: |
| * 1. It's not necessary to keep both filters all the time. The spare one can be |
| * freed after the RCU grace period and reallocated if needed again. |
| * 2. And when reallocating, it's worth scaling its size according to the number |
| * of inserted entries in the other filter, to reduce the memory overhead on |
| * small systems and false positives on large systems. |
| * 3. Jenkins' hash function is an alternative to Knuth's. |
| */ |
| #define BLOOM_FILTER_SHIFT 15 |
| |
| static inline int filter_gen_from_seq(unsigned long seq) |
| { |
| return seq % NR_BLOOM_FILTERS; |
| } |
| |
| static void get_item_key(void *item, int *key) |
| { |
| u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2); |
| |
| BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32)); |
| |
| key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1); |
| key[1] = hash >> BLOOM_FILTER_SHIFT; |
| } |
| |
| static bool test_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq, |
| void *item) |
| { |
| int key[2]; |
| unsigned long *filter; |
| int gen = filter_gen_from_seq(seq); |
| |
| filter = READ_ONCE(mm_state->filters[gen]); |
| if (!filter) |
| return true; |
| |
| get_item_key(item, key); |
| |
| return test_bit(key[0], filter) && test_bit(key[1], filter); |
| } |
| |
| static void update_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq, |
| void *item) |
| { |
| int key[2]; |
| unsigned long *filter; |
| int gen = filter_gen_from_seq(seq); |
| |
| filter = READ_ONCE(mm_state->filters[gen]); |
| if (!filter) |
| return; |
| |
| get_item_key(item, key); |
| |
| if (!test_bit(key[0], filter)) |
| set_bit(key[0], filter); |
| if (!test_bit(key[1], filter)) |
| set_bit(key[1], filter); |
| } |
| |
| static void reset_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq) |
| { |
| unsigned long *filter; |
| int gen = filter_gen_from_seq(seq); |
| |
| filter = mm_state->filters[gen]; |
| if (filter) { |
| bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT)); |
| return; |
| } |
| |
| filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT), |
| __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN); |
| WRITE_ONCE(mm_state->filters[gen], filter); |
| } |
| |
| /****************************************************************************** |
| * mm_struct list |
| ******************************************************************************/ |
| |
| #ifdef CONFIG_LRU_GEN_WALKS_MMU |
| |
| static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg) |
| { |
| static struct lru_gen_mm_list mm_list = { |
| .fifo = LIST_HEAD_INIT(mm_list.fifo), |
| .lock = __SPIN_LOCK_UNLOCKED(mm_list.lock), |
| }; |
| |
| #ifdef CONFIG_MEMCG |
| if (memcg) |
| return &memcg->mm_list; |
| #endif |
| VM_WARN_ON_ONCE(!mem_cgroup_disabled()); |
| |
| return &mm_list; |
| } |
| |
| static struct lru_gen_mm_state *get_mm_state(struct lruvec *lruvec) |
| { |
| return &lruvec->mm_state; |
| } |
| |
| static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk) |
| { |
| int key; |
| struct mm_struct *mm; |
| struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); |
| struct lru_gen_mm_state *mm_state = get_mm_state(walk->lruvec); |
| |
| mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list); |
| key = pgdat->node_id % BITS_PER_TYPE(mm->lru_gen.bitmap); |
| |
| if (!walk->force_scan && !test_bit(key, &mm->lru_gen.bitmap)) |
| return NULL; |
| |
| clear_bit(key, &mm->lru_gen.bitmap); |
| |
| return mmget_not_zero(mm) ? mm : NULL; |
| } |
| |
| void lru_gen_add_mm(struct mm_struct *mm) |
| { |
| int nid; |
| struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm); |
| struct lru_gen_mm_list *mm_list = get_mm_list(memcg); |
| |
| VM_WARN_ON_ONCE(!list_empty(&mm->lru_gen.list)); |
| #ifdef CONFIG_MEMCG |
| VM_WARN_ON_ONCE(mm->lru_gen.memcg); |
| mm->lru_gen.memcg = memcg; |
| #endif |
| spin_lock(&mm_list->lock); |
| |
| for_each_node_state(nid, N_MEMORY) { |
| struct lruvec *lruvec = get_lruvec(memcg, nid); |
| struct lru_gen_mm_state *mm_state = get_mm_state(lruvec); |
| |
| /* the first addition since the last iteration */ |
| if (mm_state->tail == &mm_list->fifo) |
| mm_state->tail = &mm->lru_gen.list; |
| } |
| |
| list_add_tail(&mm->lru_gen.list, &mm_list->fifo); |
| |
| spin_unlock(&mm_list->lock); |
| } |
| |
| void lru_gen_del_mm(struct mm_struct *mm) |
| { |
| int nid; |
| struct lru_gen_mm_list *mm_list; |
| struct mem_cgroup *memcg = NULL; |
| |
| if (list_empty(&mm->lru_gen.list)) |
| return; |
| |
| #ifdef CONFIG_MEMCG |
| memcg = mm->lru_gen.memcg; |
| #endif |
| mm_list = get_mm_list(memcg); |
| |
| spin_lock(&mm_list->lock); |
| |
| for_each_node(nid) { |
| struct lruvec *lruvec = get_lruvec(memcg, nid); |
| struct lru_gen_mm_state *mm_state = get_mm_state(lruvec); |
| |
| /* where the current iteration continues after */ |
| if (mm_state->head == &mm->lru_gen.list) |
| mm_state->head = mm_state->head->prev; |
| |
| /* where the last iteration ended before */ |
| if (mm_state->tail == &mm->lru_gen.list) |
| mm_state->tail = mm_state->tail->next; |
| } |
| |
| list_del_init(&mm->lru_gen.list); |
| |
| spin_unlock(&mm_list->lock); |
| |
| #ifdef CONFIG_MEMCG |
| mem_cgroup_put(mm->lru_gen.memcg); |
| mm->lru_gen.memcg = NULL; |
| #endif |
| } |
| |
| #ifdef CONFIG_MEMCG |
| void lru_gen_migrate_mm(struct mm_struct *mm) |
| { |
| struct mem_cgroup *memcg; |
| struct task_struct *task = rcu_dereference_protected(mm->owner, true); |
| |
| VM_WARN_ON_ONCE(task->mm != mm); |
| lockdep_assert_held(&task->alloc_lock); |
| |
| /* for mm_update_next_owner() */ |
| if (mem_cgroup_disabled()) |
| return; |
| |
| /* migration can happen before addition */ |
| if (!mm->lru_gen.memcg) |
| return; |
| |
| rcu_read_lock(); |
| memcg = mem_cgroup_from_task(task); |
| rcu_read_unlock(); |
| if (memcg == mm->lru_gen.memcg) |
| return; |
| |
| VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list)); |
| |
| lru_gen_del_mm(mm); |
| lru_gen_add_mm(mm); |
| } |
| #endif |
| |
| #else /* !CONFIG_LRU_GEN_WALKS_MMU */ |
| |
| static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg) |
| { |
| return NULL; |
| } |
| |
| static struct lru_gen_mm_state *get_mm_state(struct lruvec *lruvec) |
| { |
| return NULL; |
| } |
| |
| static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk) |
| { |
| return NULL; |
| } |
| |
| #endif |
| |
| static void reset_mm_stats(struct lru_gen_mm_walk *walk, bool last) |
| { |
| int i; |
| int hist; |
| struct lruvec *lruvec = walk->lruvec; |
| struct lru_gen_mm_state *mm_state = get_mm_state(lruvec); |
| |
| lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock); |
| |
| hist = lru_hist_from_seq(walk->seq); |
| |
| for (i = 0; i < NR_MM_STATS; i++) { |
| WRITE_ONCE(mm_state->stats[hist][i], |
| mm_state->stats[hist][i] + walk->mm_stats[i]); |
| walk->mm_stats[i] = 0; |
| } |
| |
| if (NR_HIST_GENS > 1 && last) { |
| hist = lru_hist_from_seq(walk->seq + 1); |
| |
| for (i = 0; i < NR_MM_STATS; i++) |
| WRITE_ONCE(mm_state->stats[hist][i], 0); |
| } |
| } |
| |
| static bool iterate_mm_list(struct lru_gen_mm_walk *walk, struct mm_struct **iter) |
| { |
| bool first = false; |
| bool last = false; |
| struct mm_struct *mm = NULL; |
| struct lruvec *lruvec = walk->lruvec; |
| struct mem_cgroup *memcg = lruvec_memcg(lruvec); |
| struct lru_gen_mm_list *mm_list = get_mm_list(memcg); |
| struct lru_gen_mm_state *mm_state = get_mm_state(lruvec); |
| |
| /* |
| * mm_state->seq is incremented after each iteration of mm_list. There |
| * are three interesting cases for this page table walker: |
| * 1. It tries to start a new iteration with a stale max_seq: there is |
| * nothing left to do. |
| * 2. It started the next iteration: it needs to reset the Bloom filter |
| * so that a fresh set of PTE tables can be recorded. |
| * 3. It ended the current iteration: it needs to reset the mm stats |
| * counters and tell its caller to increment max_seq. |
| */ |
| spin_lock(&mm_list->lock); |
| |
| VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->seq); |
| |
| if (walk->seq <= mm_state->seq) |
| goto done; |
| |
| if (!mm_state->head) |
| mm_state->head = &mm_list->fifo; |
| |
| if (mm_state->head == &mm_list->fifo) |
| first = true; |
| |
| do { |
| mm_state->head = mm_state->head->next; |
| if (mm_state->head == &mm_list->fifo) { |
| WRITE_ONCE(mm_state->seq, mm_state->seq + 1); |
| last = true; |
| break; |
| } |
| |
| /* force scan for those added after the last iteration */ |
| if (!mm_state->tail || mm_state->tail == mm_state->head) { |
| mm_state->tail = mm_state->head->next; |
| walk->force_scan = true; |
| } |
| } while (!(mm = get_next_mm(walk))); |
| done: |
| if (*iter || last) |
| reset_mm_stats(walk, last); |
| |
| spin_unlock(&mm_list->lock); |
| |
| if (mm && first) |
| reset_bloom_filter(mm_state, walk->seq + 1); |
| |
| if (*iter) |
| mmput_async(*iter); |
| |
| *iter = mm; |
| |
| return last; |
| } |
| |
| static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long seq) |
| { |
| bool success = false; |
| struct mem_cgroup *memcg = lruvec_memcg(lruvec); |
| struct lru_gen_mm_list *mm_list = get_mm_list(memcg); |
| struct lru_gen_mm_state *mm_state = get_mm_state(lruvec); |
| |
| spin_lock(&mm_list->lock); |
| |
| VM_WARN_ON_ONCE(mm_state->seq + 1 < seq); |
| |
| if (seq > mm_state->seq) { |
| mm_state->head = NULL; |
| mm_state->tail = NULL; |
| WRITE_ONCE(mm_state->seq, mm_state->seq + 1); |
| success = true; |
| } |
| |
| spin_unlock(&mm_list->lock); |
| |
| return success; |
| } |
| |
| /****************************************************************************** |
| * PID controller |
| ******************************************************************************/ |
| |
| /* |
| * A feedback loop based on Proportional-Integral-Derivative (PID) controller. |
| * |
| * The P term is refaulted/(evicted+protected) from a tier in the generation |
| * currently being evicted; the I term is the exponential moving average of the |
| * P term over the generations previously evicted, using the smoothing factor |
| * 1/2; the D term isn't supported. |
| * |
| * The setpoint (SP) is always the first tier of one type; the process variable |
| * (PV) is either any tier of the other type or any other tier of the same |
| * type. |
| * |
| * The error is the difference between the SP and the PV; the correction is to |
| * turn off protection when SP>PV or turn on protection when SP<PV. |
| * |
| * For future optimizations: |
| * 1. The D term may discount the other two terms over time so that long-lived |
| * generations can resist stale information. |
| */ |
| struct ctrl_pos { |
| unsigned long refaulted; |
| unsigned long total; |
| int gain; |
| }; |
| |
| static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain, |
| struct ctrl_pos *pos) |
| { |
| struct lru_gen_folio *lrugen = &lruvec->lrugen; |
| int hist = lru_hist_from_seq(lrugen->min_seq[type]); |
| |
| pos->refaulted = lrugen->avg_refaulted[type][tier] + |
| atomic_long_read(&lrugen->refaulted[hist][type][tier]); |
| pos->total = lrugen->avg_total[type][tier] + |
| atomic_long_read(&lrugen->evicted[hist][type][tier]); |
| if (tier) |
| pos->total += lrugen->protected[hist][type][tier - 1]; |
| pos->gain = gain; |
| } |
| |
| static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover) |
| { |
| int hist, tier; |
| struct lru_gen_folio *lrugen = &lruvec->lrugen; |
| bool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS > 1; |
| unsigned long seq = carryover ? lrugen->min_seq[type] : lrugen->max_seq + 1; |
| |
| lockdep_assert_held(&lruvec->lru_lock); |
| |
| if (!carryover && !clear) |
| return; |
| |
| hist = lru_hist_from_seq(seq); |
| |
| for (tier = 0; tier < MAX_NR_TIERS; tier++) { |
| if (carryover) { |
| unsigned long sum; |
| |
| sum = lrugen->avg_refaulted[type][tier] + |
| atomic_long_read(&lrugen->refaulted[hist][type][tier]); |
| WRITE_ONCE(lrugen->avg_refaulted[type][tier], sum / 2); |
| |
| sum = lrugen->avg_total[type][tier] + |
| atomic_long_read(&lrugen->evicted[hist][type][tier]); |
| if (tier) |
| sum += lrugen->protected[hist][type][tier - 1]; |
| WRITE_ONCE(lrugen->avg_total[type][tier], sum / 2); |
| } |
| |
| if (clear) { |
| atomic_long_set(&lrugen->refaulted[hist][type][tier], 0); |
| atomic_long_set(&lrugen->evicted[hist][type][tier], 0); |
| if (tier) |
| WRITE_ONCE(lrugen->protected[hist][type][tier - 1], 0); |
| } |
| } |
| } |
| |
| static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv) |
| { |
| /* |
| * Return true if the PV has a limited number of refaults or a lower |
| * refaulted/total than the SP. |
| */ |
| return pv->refaulted < MIN_LRU_BATCH || |
| pv->refaulted * (sp->total + MIN_LRU_BATCH) * sp->gain <= |
| (sp->refaulted + 1) * pv->total * pv->gain; |
| } |
| |
| /****************************************************************************** |
| * the aging |
| ******************************************************************************/ |
| |
| /* promote pages accessed through page tables */ |
| static int folio_update_gen(struct folio *folio, int gen) |
| { |
| unsigned long new_flags, old_flags = READ_ONCE(folio->flags); |
| |
| VM_WARN_ON_ONCE(gen >= MAX_NR_GENS); |
| VM_WARN_ON_ONCE(!rcu_read_lock_held()); |
| |
| do { |
| /* lru_gen_del_folio() has isolated this page? */ |
| if (!(old_flags & LRU_GEN_MASK)) { |
| /* for shrink_folio_list() */ |
| new_flags = old_flags | BIT(PG_referenced); |
| continue; |
| } |
| |
| new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS); |
| new_flags |= (gen + 1UL) << LRU_GEN_PGOFF; |
| } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags)); |
| |
| return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; |
| } |
| |
| /* protect pages accessed multiple times through file descriptors */ |
| static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming) |
| { |
| int type = folio_is_file_lru(folio); |
| struct lru_gen_folio *lrugen = &lruvec->lrugen; |
| int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); |
| unsigned long new_flags, old_flags = READ_ONCE(folio->flags); |
| |
| VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio); |
| |
| do { |
| new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; |
| /* folio_update_gen() has promoted this page? */ |
| if (new_gen >= 0 && new_gen != old_gen) |
| return new_gen; |
| |
| new_gen = (old_gen + 1) % MAX_NR_GENS; |
| |
| new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS); |
| new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF; |
| /* for folio_end_writeback() */ |
| if (reclaiming) |
| new_flags |= BIT(PG_reclaim); |
| } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags)); |
| |
| lru_gen_update_size(lruvec, folio, old_gen, new_gen); |
| |
| return new_gen; |
| } |
| |
| static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio, |
| int old_gen, int new_gen) |
| { |
| int type = folio_is_file_lru(folio); |
| int zone = folio_zonenum(folio); |
| int delta = folio_nr_pages(folio); |
| |
| VM_WARN_ON_ONCE(old_gen >= MAX_NR_GENS); |
| VM_WARN_ON_ONCE(new_gen >= MAX_NR_GENS); |
| |
| walk->batched++; |
| |
| walk->nr_pages[old_gen][type][zone] -= delta; |
| walk->nr_pages[new_gen][type][zone] += delta; |
| } |
| |
| static void reset_batch_size(struct lru_gen_mm_walk *walk) |
| { |
| int gen, type, zone; |
| struct lruvec *lruvec = walk->lruvec; |
| struct lru_gen_folio *lrugen = &lruvec->lrugen; |
| |
| walk->batched = 0; |
| |
| for_each_gen_type_zone(gen, type, zone) { |
| enum lru_list lru = type * LRU_INACTIVE_FILE; |
| int delta = walk->nr_pages[gen][type][zone]; |
| |
| if (!delta) |
| continue; |
| |
| walk->nr_pages[gen][type][zone] = 0; |
| WRITE_ONCE(lrugen->nr_pages[gen][type][zone], |
| lrugen->nr_pages[gen][type][zone] + delta); |
| |
| if (lru_gen_is_active(lruvec, gen)) |
| lru += LRU_ACTIVE; |
| __update_lru_size(lruvec, lru, zone, delta); |
| } |
| } |
| |
| static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *args) |
| { |
| struct address_space *mapping; |
| struct vm_area_struct *vma = args->vma; |
| struct lru_gen_mm_walk *walk = args->private; |
| |
| if (!vma_is_accessible(vma)) |
| return true; |
| |
| if (is_vm_hugetlb_page(vma)) |
| return true; |
| |
| if (!vma_has_recency(vma)) |
| return true; |
| |
| if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) |
| return true; |
| |
| if (vma == get_gate_vma(vma->vm_mm)) |
| return true; |
| |
| if (vma_is_anonymous(vma)) |
| return !walk->can_swap; |
| |
| if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping)) |
| return true; |
| |
| mapping = vma->vm_file->f_mapping; |
| if (mapping_unevictable(mapping)) |
| return true; |
| |
| if (shmem_mapping(mapping)) |
| return !walk->can_swap; |
| |
| /* to exclude special mappings like dax, etc. */ |
| return !mapping->a_ops->read_folio; |
| } |
| |
| /* |
| * Some userspace memory allocators map many single-page VMAs. Instead of |
| * returning back to the PGD table for each of such VMAs, finish an entire PMD |
| * table to reduce zigzags and improve cache performance. |
| */ |
| static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk *args, |
| unsigned long *vm_start, unsigned long *vm_end) |
| { |
| unsigned long start = round_up(*vm_end, size); |
| unsigned long end = (start | ~mask) + 1; |
| VMA_ITERATOR(vmi, args->mm, start); |
| |
| VM_WARN_ON_ONCE(mask & size); |
| VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask)); |
| |
| for_each_vma(vmi, args->vma) { |
| if (end && end <= args->vma->vm_start) |
| return false; |
|