| // 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 try_to_release_page(), |
| 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/rwsem.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/oom.h> |
| #include <linux/pagevec.h> |
| #include <linux/prefetch.h> |
| #include <linux/printk.h> |
| #include <linux/dax.h> |
| #include <linux/psi.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; |
| |
| /* Can active pages 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 pages be reclaimed? */ |
| unsigned int may_unmap:1; |
| |
| /* Can pages be swapped as part of reclaim? */ |
| unsigned int may_swap: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; |
| |
| 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 pages 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 pages 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_page(_page, _base, _field) \ |
| do { \ |
| if ((_page)->lru.prev != _base) { \ |
| struct page *prev; \ |
| \ |
| prev = lru_to_page(&(_page->lru)); \ |
| prefetchw(&prev->_field); \ |
| } \ |
| } while (0) |
| #else |
| #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) |
| #endif |
| |
| /* |
| * From 0 .. 200. Higher means more swappy. |
| */ |
| int vm_swappiness = 60; |
| |
| 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; |
| } |
| |
| static LIST_HEAD(shrinker_list); |
| static DECLARE_RWSEM(shrinker_rwsem); |
| |
| #ifdef CONFIG_MEMCG |
| static int shrinker_nr_max; |
| |
| /* The shrinker_info is expanded in a batch of BITS_PER_LONG */ |
| static inline int shrinker_map_size(int nr_items) |
| { |
| return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long)); |
| } |
| |
| static inline int shrinker_defer_size(int nr_items) |
| { |
| return (round_up(nr_items, BITS_PER_LONG) * sizeof(atomic_long_t)); |
| } |
| |
| static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg, |
| int nid) |
| { |
| return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info, |
| lockdep_is_held(&shrinker_rwsem)); |
| } |
| |
| static int expand_one_shrinker_info(struct mem_cgroup *memcg, |
| int map_size, int defer_size, |
| int old_map_size, int old_defer_size) |
| { |
| struct shrinker_info *new, *old; |
| struct mem_cgroup_per_node *pn; |
| int nid; |
| int size = map_size + defer_size; |
| |
| for_each_node(nid) { |
| pn = memcg->nodeinfo[nid]; |
| old = shrinker_info_protected(memcg, nid); |
| /* Not yet online memcg */ |
| if (!old) |
| return 0; |
| |
| new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid); |
| if (!new) |
| return -ENOMEM; |
| |
| new->nr_deferred = (atomic_long_t *)(new + 1); |
| new->map = (void *)new->nr_deferred + defer_size; |
| |
| /* map: set all old bits, clear all new bits */ |
| memset(new->map, (int)0xff, old_map_size); |
| memset((void *)new->map + old_map_size, 0, map_size - old_map_size); |
| /* nr_deferred: copy old values, clear all new values */ |
| memcpy(new->nr_deferred, old->nr_deferred, old_defer_size); |
| memset((void *)new->nr_deferred + old_defer_size, 0, |
| defer_size - old_defer_size); |
| |
| rcu_assign_pointer(pn->shrinker_info, new); |
| kvfree_rcu(old, rcu); |
| } |
| |
| return 0; |
| } |
| |
| void free_shrinker_info(struct mem_cgroup *memcg) |
| { |
| struct mem_cgroup_per_node *pn; |
| struct shrinker_info *info; |
| int nid; |
| |
| for_each_node(nid) { |
| pn = memcg->nodeinfo[nid]; |
| info = rcu_dereference_protected(pn->shrinker_info, true); |
| kvfree(info); |
| rcu_assign_pointer(pn->shrinker_info, NULL); |
| } |
| } |
| |
| int alloc_shrinker_info(struct mem_cgroup *memcg) |
| { |
| struct shrinker_info *info; |
| int nid, size, ret = 0; |
| int map_size, defer_size = 0; |
| |
| down_write(&shrinker_rwsem); |
| map_size = shrinker_map_size(shrinker_nr_max); |
| defer_size = shrinker_defer_size(shrinker_nr_max); |
| size = map_size + defer_size; |
| for_each_node(nid) { |
| info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid); |
| if (!info) { |
| free_shrinker_info(memcg); |
| ret = -ENOMEM; |
| break; |
| } |
| info->nr_deferred = (atomic_long_t *)(info + 1); |
| info->map = (void *)info->nr_deferred + defer_size; |
| rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info); |
| } |
| up_write(&shrinker_rwsem); |
| |
| return ret; |
| } |
| |
| static inline bool need_expand(int nr_max) |
| { |
| return round_up(nr_max, BITS_PER_LONG) > |
| round_up(shrinker_nr_max, BITS_PER_LONG); |
| } |
| |
| static int expand_shrinker_info(int new_id) |
| { |
| int ret = 0; |
| int new_nr_max = new_id + 1; |
| int map_size, defer_size = 0; |
| int old_map_size, old_defer_size = 0; |
| struct mem_cgroup *memcg; |
| |
| if (!need_expand(new_nr_max)) |
| goto out; |
| |
| if (!root_mem_cgroup) |
| goto out; |
| |
| lockdep_assert_held(&shrinker_rwsem); |
| |
| map_size = shrinker_map_size(new_nr_max); |
| defer_size = shrinker_defer_size(new_nr_max); |
| old_map_size = shrinker_map_size(shrinker_nr_max); |
| old_defer_size = shrinker_defer_size(shrinker_nr_max); |
| |
| memcg = mem_cgroup_iter(NULL, NULL, NULL); |
| do { |
| ret = expand_one_shrinker_info(memcg, map_size, defer_size, |
| old_map_size, old_defer_size); |
| if (ret) { |
| mem_cgroup_iter_break(NULL, memcg); |
| goto out; |
| } |
| } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); |
| out: |
| if (!ret) |
| shrinker_nr_max = new_nr_max; |
| |
| return ret; |
| } |
| |
| void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) |
| { |
| if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) { |
| struct shrinker_info *info; |
| |
| rcu_read_lock(); |
| info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info); |
| /* Pairs with smp mb in shrink_slab() */ |
| smp_mb__before_atomic(); |
| set_bit(shrinker_id, info->map); |
| rcu_read_unlock(); |
| } |
| } |
| |
| static DEFINE_IDR(shrinker_idr); |
| |
| static int prealloc_memcg_shrinker(struct shrinker *shrinker) |
| { |
| int id, ret = -ENOMEM; |
| |
| if (mem_cgroup_disabled()) |
| return -ENOSYS; |
| |
| down_write(&shrinker_rwsem); |
| /* This may call shrinker, so it must use down_read_trylock() */ |
| id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); |
| if (id < 0) |
| goto unlock; |
| |
| if (id >= shrinker_nr_max) { |
| if (expand_shrinker_info(id)) { |
| idr_remove(&shrinker_idr, id); |
| goto unlock; |
| } |
| } |
| shrinker->id = id; |
| ret = 0; |
| unlock: |
| up_write(&shrinker_rwsem); |
| return ret; |
| } |
| |
| static void unregister_memcg_shrinker(struct shrinker *shrinker) |
| { |
| int id = shrinker->id; |
| |
| BUG_ON(id < 0); |
| |
| lockdep_assert_held(&shrinker_rwsem); |
| |
| idr_remove(&shrinker_idr, id); |
| } |
| |
| static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker, |
| struct mem_cgroup *memcg) |
| { |
| struct shrinker_info *info; |
| |
| info = shrinker_info_protected(memcg, nid); |
| return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0); |
| } |
| |
| static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker, |
| struct mem_cgroup *memcg) |
| { |
| struct shrinker_info *info; |
| |
| info = shrinker_info_protected(memcg, nid); |
| return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]); |
| } |
| |
| void reparent_shrinker_deferred(struct mem_cgroup *memcg) |
| { |
| int i, nid; |
| long nr; |
| struct mem_cgroup *parent; |
| struct shrinker_info *child_info, *parent_info; |
| |
| parent = parent_mem_cgroup(memcg); |
| if (!parent) |
| parent = root_mem_cgroup; |
| |
| /* Prevent from concurrent shrinker_info expand */ |
| down_read(&shrinker_rwsem); |
| for_each_node(nid) { |
| child_info = shrinker_info_protected(memcg, nid); |
| parent_info = shrinker_info_protected(parent, nid); |
| for (i = 0; i < shrinker_nr_max; i++) { |
| nr = atomic_long_read(&child_info->nr_deferred[i]); |
| atomic_long_add(nr, &parent_info->nr_deferred[i]); |
| } |
| } |
| up_read(&shrinker_rwsem); |
| } |
| |
| static bool cgroup_reclaim(struct scan_control *sc) |
| { |
| return 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_page_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; |
| } |
| #else |
| static int prealloc_memcg_shrinker(struct shrinker *shrinker) |
| { |
| return -ENOSYS; |
| } |
| |
| static void unregister_memcg_shrinker(struct shrinker *shrinker) |
| { |
| } |
| |
| static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker, |
| struct mem_cgroup *memcg) |
| { |
| return 0; |
| } |
| |
| static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker, |
| struct mem_cgroup *memcg) |
| { |
| return 0; |
| } |
| |
| static bool cgroup_reclaim(struct scan_control *sc) |
| { |
| return false; |
| } |
| |
| static bool writeback_throttling_sane(struct scan_control *sc) |
| { |
| return true; |
| } |
| #endif |
| |
| static long xchg_nr_deferred(struct shrinker *shrinker, |
| struct shrink_control *sc) |
| { |
| int nid = sc->nid; |
| |
| if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) |
| nid = 0; |
| |
| if (sc->memcg && |
| (shrinker->flags & SHRINKER_MEMCG_AWARE)) |
| return xchg_nr_deferred_memcg(nid, shrinker, |
| sc->memcg); |
| |
| return atomic_long_xchg(&shrinker->nr_deferred[nid], 0); |
| } |
| |
| |
| static long add_nr_deferred(long nr, struct shrinker *shrinker, |
| struct shrink_control *sc) |
| { |
| int nid = sc->nid; |
| |
| if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) |
| nid = 0; |
| |
| if (sc->memcg && |
| (shrinker->flags & SHRINKER_MEMCG_AWARE)) |
| return add_nr_deferred_memcg(nr, nid, shrinker, |
| sc->memcg); |
| |
| return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]); |
| } |
| |
| 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 pages which are not accounted for to save counters. |
| * As the data only determines if reclaim or compaction continues, it is |
| * not expected that isolated pages 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; |
| } |
| |
| /* |
| * Add a shrinker callback to be called from the vm. |
| */ |
| int prealloc_shrinker(struct shrinker *shrinker) |
| { |
| unsigned int size; |
| int err; |
| |
| if (shrinker->flags & SHRINKER_MEMCG_AWARE) { |
| err = prealloc_memcg_shrinker(shrinker); |
| if (err != -ENOSYS) |
| return err; |
| |
| shrinker->flags &= ~SHRINKER_MEMCG_AWARE; |
| } |
| |
| size = sizeof(*shrinker->nr_deferred); |
| if (shrinker->flags & SHRINKER_NUMA_AWARE) |
| size *= nr_node_ids; |
| |
| shrinker->nr_deferred = kzalloc(size, GFP_KERNEL); |
| if (!shrinker->nr_deferred) |
| return -ENOMEM; |
| |
| return 0; |
| } |
| |
| void free_prealloced_shrinker(struct shrinker *shrinker) |
| { |
| if (shrinker->flags & SHRINKER_MEMCG_AWARE) { |
| down_write(&shrinker_rwsem); |
| unregister_memcg_shrinker(shrinker); |
| up_write(&shrinker_rwsem); |
| return; |
| } |
| |
| kfree(shrinker->nr_deferred); |
| shrinker->nr_deferred = NULL; |
| } |
| |
| void register_shrinker_prepared(struct shrinker *shrinker) |
| { |
| down_write(&shrinker_rwsem); |
| list_add_tail(&shrinker->list, &shrinker_list); |
| shrinker->flags |= SHRINKER_REGISTERED; |
| up_write(&shrinker_rwsem); |
| } |
| |
| int register_shrinker(struct shrinker *shrinker) |
| { |
| int err = prealloc_shrinker(shrinker); |
| |
| if (err) |
| return err; |
| register_shrinker_prepared(shrinker); |
| return 0; |
| } |
| EXPORT_SYMBOL(register_shrinker); |
| |
| /* |
| * Remove one |
| */ |
| void unregister_shrinker(struct shrinker *shrinker) |
| { |
| if (!(shrinker->flags & SHRINKER_REGISTERED)) |
| return; |
| |
| down_write(&shrinker_rwsem); |
| list_del(&shrinker->list); |
| shrinker->flags &= ~SHRINKER_REGISTERED; |
| if (shrinker->flags & SHRINKER_MEMCG_AWARE) |
| unregister_memcg_shrinker(shrinker); |
| up_write(&shrinker_rwsem); |
| |
| kfree(shrinker->nr_deferred); |
| shrinker->nr_deferred = NULL; |
| } |
| EXPORT_SYMBOL(unregister_shrinker); |
| |
| /** |
| * synchronize_shrinkers - Wait for all running shrinkers to complete. |
| * |
| * This is equivalent to calling unregister_shrink() and register_shrinker(), |
| * but atomically and with less overhead. This is useful to guarantee that all |
| * shrinker invocations have seen an update, before freeing memory, similar to |
| * rcu. |
| */ |
| void synchronize_shrinkers(void) |
| { |
| down_write(&shrinker_rwsem); |
| up_write(&shrinker_rwsem); |
| } |
| EXPORT_SYMBOL(synchronize_shrinkers); |
| |
| #define SHRINK_BATCH 128 |
| |
| static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, |
| struct shrinker *shrinker, int priority) |
| { |
| unsigned long freed = 0; |
| unsigned long long delta; |
| long total_scan; |
| long freeable; |
| long nr; |
| long new_nr; |
| long batch_size = shrinker->batch ? shrinker->batch |
| : SHRINK_BATCH; |
| long scanned = 0, next_deferred; |
| |
| freeable = shrinker->count_objects(shrinker, shrinkctl); |
| if (freeable == 0 || freeable == SHRINK_EMPTY) |
| return freeable; |
| |
| /* |
| * copy the current shrinker scan count into a local variable |
| * and zero it so that other concurrent shrinker invocations |
| * don't also do this scanning work. |
| */ |
| nr = xchg_nr_deferred(shrinker, shrinkctl); |
| |
| if (shrinker->seeks) { |
| delta = freeable >> priority; |
| delta *= 4; |
| do_div(delta, shrinker->seeks); |
| } else { |
| /* |
| * These objects don't require any IO to create. Trim |
| * them aggressively under memory pressure to keep |
| * them from causing refetches in the IO caches. |
| */ |
| delta = freeable / 2; |
| } |
| |
| total_scan = nr >> priority; |
| total_scan += delta; |
| total_scan = min(total_scan, (2 * freeable)); |
| |
| trace_mm_shrink_slab_start(shrinker, shrinkctl, nr, |
| freeable, delta, total_scan, priority); |
| |
| /* |
| * Normally, we should not scan less than batch_size objects in one |
| * pass to avoid too frequent shrinker calls, but if the slab has less |
| * than batch_size objects in total and we are really tight on memory, |
| * we will try to reclaim all available objects, otherwise we can end |
| * up failing allocations although there are plenty of reclaimable |
| * objects spread over several slabs with usage less than the |
| * batch_size. |
| * |
| * We detect the "tight on memory" situations by looking at the total |
| * number of objects we want to scan (total_scan). If it is greater |
| * than the total number of objects on slab (freeable), we must be |
| * scanning at high prio and therefore should try to reclaim as much as |
| * possible. |
| */ |
| while (total_scan >= batch_size || |
| total_scan >= freeable) { |
| unsigned long ret; |
| unsigned long nr_to_scan = min(batch_size, total_scan); |
| |
| shrinkctl->nr_to_scan = nr_to_scan; |
| shrinkctl->nr_scanned = nr_to_scan; |
| ret = shrinker->scan_objects(shrinker, shrinkctl); |
| if (ret == SHRINK_STOP) |
| break; |
| freed += ret; |
| |
| count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned); |
| total_scan -= shrinkctl->nr_scanned; |
| scanned += shrinkctl->nr_scanned; |
| |
| cond_resched(); |
| } |
| |
| /* |
| * The deferred work is increased by any new work (delta) that wasn't |
| * done, decreased by old deferred work that was done now. |
| * |
| * And it is capped to two times of the freeable items. |
| */ |
| next_deferred = max_t(long, (nr + delta - scanned), 0); |
| next_deferred = min(next_deferred, (2 * freeable)); |
| |
| /* |
| * move the unused scan count back into the shrinker in a |
| * manner that handles concurrent updates. |
| */ |
| new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl); |
| |
| trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan); |
| return freed; |
| } |
| |
| #ifdef CONFIG_MEMCG |
| static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, |
| struct mem_cgroup *memcg, int priority) |
| { |
| struct shrinker_info *info; |
| unsigned long ret, freed = 0; |
| int i; |
| |
| if (!mem_cgroup_online(memcg)) |
| return 0; |
| |
| if (!down_read_trylock(&shrinker_rwsem)) |
| return 0; |
| |
| info = shrinker_info_protected(memcg, nid); |
| if (unlikely(!info)) |
| goto unlock; |
| |
| for_each_set_bit(i, info->map, shrinker_nr_max) { |
| struct shrink_control sc = { |
| .gfp_mask = gfp_mask, |
| .nid = nid, |
| .memcg = memcg, |
| }; |
| struct shrinker *shrinker; |
| |
| shrinker = idr_find(&shrinker_idr, i); |
| if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) { |
| if (!shrinker) |
| clear_bit(i, info->map); |
| continue; |
| } |
| |
| /* Call non-slab shrinkers even though kmem is disabled */ |
| if (!memcg_kmem_enabled() && |
| !(shrinker->flags & SHRINKER_NONSLAB)) |
| continue; |
| |
| ret = do_shrink_slab(&sc, shrinker, priority); |
| if (ret == SHRINK_EMPTY) { |
| clear_bit(i, info->map); |
| /* |
| * After the shrinker reported that it had no objects to |
| * free, but before we cleared the corresponding bit in |
| * the memcg shrinker map, a new object might have been |
| * added. To make sure, we have the bit set in this |
| * case, we invoke the shrinker one more time and reset |
| * the bit if it reports that it is not empty anymore. |
| * The memory barrier here pairs with the barrier in |
| * set_shrinker_bit(): |
| * |
| * list_lru_add() shrink_slab_memcg() |
| * list_add_tail() clear_bit() |
| * <MB> <MB> |
| * set_bit() do_shrink_slab() |
| */ |
| smp_mb__after_atomic(); |
| ret = do_shrink_slab(&sc, shrinker, priority); |
| if (ret == SHRINK_EMPTY) |
| ret = 0; |
| else |
| set_shrinker_bit(memcg, nid, i); |
| } |
| freed += ret; |
| |
| if (rwsem_is_contended(&shrinker_rwsem)) { |
| freed = freed ? : 1; |
| break; |
| } |
| } |
| unlock: |
| up_read(&shrinker_rwsem); |
| return freed; |
| } |
| #else /* CONFIG_MEMCG */ |
| static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, |
| struct mem_cgroup *memcg, int priority) |
| { |
| return 0; |
| } |
| #endif /* CONFIG_MEMCG */ |
| |
| /** |
| * shrink_slab - shrink slab caches |
| * @gfp_mask: allocation context |
| * @nid: node whose slab caches to target |
| * @memcg: memory cgroup whose slab caches to target |
| * @priority: the reclaim priority |
| * |
| * Call the shrink functions to age shrinkable caches. |
| * |
| * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set, |
| * unaware shrinkers will receive a node id of 0 instead. |
| * |
| * @memcg specifies the memory cgroup to target. Unaware shrinkers |
| * are called only if it is the root cgroup. |
| * |
| * @priority is sc->priority, we take the number of objects and >> by priority |
| * in order to get the scan target. |
| * |
| * Returns the number of reclaimed slab objects. |
| */ |
| static unsigned long shrink_slab(gfp_t gfp_mask, int nid, |
| struct mem_cgroup *memcg, |
| int priority) |
| { |
| unsigned long ret, freed = 0; |
| struct shrinker *shrinker; |
| |
| /* |
| * The root memcg might be allocated even though memcg is disabled |
| * via "cgroup_disable=memory" boot parameter. This could make |
| * mem_cgroup_is_root() return false, then just run memcg slab |
| * shrink, but skip global shrink. This may result in premature |
| * oom. |
| */ |
| if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg)) |
| return shrink_slab_memcg(gfp_mask, nid, memcg, priority); |
| |
| if (!down_read_trylock(&shrinker_rwsem)) |
| goto out; |
| |
| list_for_each_entry(shrinker, &shrinker_list, list) { |
| struct shrink_control sc = { |
| .gfp_mask = gfp_mask, |
| .nid = nid, |
| .memcg = memcg, |
| }; |
| |
| ret = do_shrink_slab(&sc, shrinker, priority); |
| if (ret == SHRINK_EMPTY) |
| ret = 0; |
| freed += ret; |
| /* |
| * Bail out if someone want to register a new shrinker to |
| * prevent the registration from being stalled for long periods |
| * by parallel ongoing shrinking. |
| */ |
| if (rwsem_is_contended(&shrinker_rwsem)) { |
| freed = freed ? : 1; |
| break; |
| } |
| } |
| |
| up_read(&shrinker_rwsem); |
| out: |
| cond_resched(); |
| return freed; |
| } |
| |
| static void drop_slab_node(int nid) |
| { |
| unsigned long freed; |
| int shift = 0; |
| |
| do { |
| struct mem_cgroup *memcg = NULL; |
| |
| if (fatal_signal_pending(current)) |
| return; |
| |
| freed = 0; |
| 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); |
| } while ((freed >> shift++) > 1); |
| } |
| |
| void drop_slab(void) |
| { |
| int nid; |
| |
| for_each_online_node(nid) |
| drop_slab_node(nid); |
| } |
| |
| static inline int is_page_cache_freeable(struct folio *folio) |
| { |
| /* |
| * A freeable page cache page is referenced only by the caller |
| * that isolated the page, the page cache and optional buffer |
| * heads at page->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 pages then do not |
| * throttle as throttling will occur when the pages 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 IO 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_IO_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 references pages 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 pages written if tasks are throttled waiting on dirty |
| * pages to clean. If enough pages 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 page out, page is locked */ |
| PAGE_KEEP, |
| /* move page to the active list, page is locked */ |
| PAGE_ACTIVATE, |
| /* page has been sent to the disk successfully, page is unlocked */ |
| PAGE_SUCCESS, |
| /* page is clean and locked */ |
| PAGE_CLEAN, |
| } pageout_t; |
| |
| /* |
| * pageout is called by shrink_page_list() for each dirty page. |
| * 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 page 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 page. |
| * |
| * Must be careful with the order of the tests. When someone has |
| * a ref to the page, it may be possible that they dirty it then |
| * drop the reference. So if PageDirty is tested before page_count |
| * here, then the following race may occur: |
| * |
| * get_user_pages(&page); |
| * [user mapping goes away] |
| * write_to(page); |
| * !PageDirty(page) [good] |
| * SetPageDirty(page); |
| * put_page(page); |
| * !page_count(page) [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 page->flags |
| * load is not satisfied before that of page->_refcount. |
| * |
| * Note that if SetPageDirty is always performed via set_page_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 page_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_entry(folio); |
| mem_cgroup_swapout(folio, swap); |
| if (reclaimed && !mapping_exiting(mapping)) |
| shadow = workingset_eviction(folio, target_memcg); |
| __delete_from_swap_cache(&folio->page, swap, shadow); |
| xa_unlock_irq(&mapping->i_pages); |
| put_swap_page(&folio->page, 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 pages 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 page_references { |
| PAGEREF_RECLAIM, |
| PAGEREF_RECLAIM_CLEAN, |
| PAGEREF_KEEP, |
| PAGEREF_ACTIVATE, |
| }; |
| |
| static enum page_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 PAGEREF_ACTIVATE; |
| |
| /* rmap lock contention: rotate */ |
| if (referenced_ptes == -1) |
| return PAGEREF_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 PAGEREF_ACTIVATE; |
| |
| /* |
| * Activate file-backed executable folios after first usage. |
| */ |
| if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) |
| return PAGEREF_ACTIVATE; |
| |
| return PAGEREF_KEEP; |
| } |
| |
| /* Reclaim if clean, defer dirty folios to writeback */ |
| if (referenced_folio && folio_is_file_lru(folio)) |
| return PAGEREF_RECLAIM_CLEAN; |
| |
| return PAGEREF_RECLAIM; |
| } |
| |
| /* Check if a page is dirty or under writeback */ |
| static void folio_check_dirty_writeback(struct folio *folio, |
| bool *dirty, bool *writeback) |
| { |
| struct address_space *mapping; |
| |
| /* |
| * Anonymous pages are not handled by flushers and must be written |
| * from reclaim context. Do not stall reclaim based on them. |
| * MADV_FREE anonymous pages 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); |
| } |
| |
| static struct page *alloc_demote_page(struct page *page, unsigned long node) |
| { |
| 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_THISNODE | __GFP_NOWARN | |
| __GFP_NOMEMALLOC | GFP_NOWAIT, |
| .nid = node |
| }; |
| |
| return alloc_migration_target(page, (unsigned long)&mtc); |
| } |
| |
| /* |
| * Take pages on @demote_list and attempt to demote them to |
| * another node. Pages which are not demoted are left on |
| * @demote_pages. |
| */ |
| static unsigned int demote_page_list(struct list_head *demote_pages, |
| struct pglist_data *pgdat) |
| { |
| int target_nid = next_demotion_node(pgdat->node_id); |
| unsigned int nr_succeeded; |
| |
| if (list_empty(demote_pages)) |
| return 0; |
| |
| if (target_nid == NUMA_NO_NODE) |
| return 0; |
| |
| /* Demotion ignores all cpuset and mempolicy settings */ |
| migrate_pages(demote_pages, alloc_demote_page, NULL, |
| target_nid, MIGRATE_ASYNC, MR_DEMOTION, |
| &nr_succeeded); |
| |
| if (current_is_kswapd()) |
| __count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded); |
| else |
| __count_vm_events(PGDEMOTE_DIRECT, 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(page_swap_flags(&folio->page) & SWP_FS_OPS); |
| } |
| |
| /* |
| * shrink_page_list() returns the number of reclaimed pages |
| */ |
| static unsigned int shrink_page_list(struct list_head *page_list, |
| struct pglist_data *pgdat, |
| struct scan_control *sc, |
| struct reclaim_stat *stat, |
| bool ignore_references) |
| { |
| LIST_HEAD(ret_pages); |
| LIST_HEAD(free_pages); |
| LIST_HEAD(demote_pages); |
| unsigned int nr_reclaimed = 0; |
| unsigned int pgactivate = 0; |
| bool do_demote_pass; |
| struct swap_iocb *plug = NULL; |
| |
| memset(stat, 0, sizeof(*stat)); |
| cond_resched(); |
| do_demote_pass = can_demote(pgdat->node_id, sc); |
| |
| retry: |
| while (!list_empty(page_list)) { |
| struct address_space *mapping; |
| struct folio *folio; |
| enum page_references references = PAGEREF_RECLAIM; |
| bool dirty, writeback; |
| unsigned int nr_pages; |
| |
| cond_resched(); |
| |
| folio = lru_to_folio(page_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; |
| |
| /* |
| * 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, page_list); |
| continue; |
| } |
| } |
| |
| if (!ignore_references) |
| references = folio_check_references(folio, sc); |
| |
| switch (references) { |
| case PAGEREF_ACTIVATE: |
| goto activate_locked; |
| case PAGEREF_KEEP: |
| stat->nr_ref_keep += nr_pages; |
| goto keep_locked; |
| case PAGEREF_RECLAIM: |
| case PAGEREF_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_pages); |
| 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 folios without a PMD map right |
| * away. Chances are some or all of the |
| * tail pages can be freed without IO. |
| */ |
| if (!folio_entire_mapcount(folio) && |
| split_folio_to_list(folio, |
| page_list)) |
| goto activate_locked; |
| } |
| if (!add_to_swap(folio)) { |
| if (!folio_test_large(folio)) |
| goto activate_locked_split; |
| /* Fallback to swap normal pages */ |
| if (split_folio_to_list(folio, |
| page_list)) |
| goto activate_locked; |
| #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| count_vm_event(THP_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, page_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; |
| |
| 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; |
| } |
| } |
| |
| 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 deactivate_page() |
| * 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 == PAGEREF_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_has_private(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; |
| |
| /* |
| * Is there need to periodically free_page_list? It would |
| * appear not as the counts should be low |
| */ |
| if (unlikely(folio_test_large(folio))) |
| destroy_compound_page(&folio->page); |
| else |
| list_add(&folio->lru, &free_pages); |
| 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->page) || |
| folio_test_mlocked(folio))) |
| try_to_free_swap(&folio->page); |
| 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_pages); |
| VM_BUG_ON_FOLIO(folio_test_lru(folio) || |
| folio_test_unevictable(folio), folio); |
| } |
| /* 'page_list' is always empty here */ |
| |
| /* Migrate folios selected for demotion */ |
| nr_reclaimed += demote_page_list(&demote_pages, pgdat); |
| /* Folios that could not be demoted are still in @demote_pages */ |
| if (!list_empty(&demote_pages)) { |
| /* Folios which weren't demoted go back on @page_list for retry: */ |
| list_splice_init(&demote_pages, page_list); |
| do_demote_pass = false; |
| goto retry; |
| } |
| |
| pgactivate = stat->nr_activate[0] + stat->nr_activate[1]; |
| |
| mem_cgroup_uncharge_list(&free_pages); |
| try_to_unmap_flush(); |
| free_unref_page_list(&free_pages); |
| |
| list_splice(&ret_pages, page_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 *page_list) |
| { |
| struct scan_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .may_unmap = 1, |
| }; |
| struct reclaim_stat stat; |
| unsigned int nr_reclaimed; |
| struct page *page, *next; |
| LIST_HEAD(clean_pages); |
| unsigned int noreclaim_flag; |
| |
| list_for_each_entry_safe(page, next, page_list, lru) { |
| if (!PageHuge(page) && page_is_file_lru(page) && |
| !PageDirty(page) && !__PageMovable(page) && |
| !PageUnevictable(page)) { |
| ClearPageActive(page); |
| list_move(&page->lru, &clean_pages); |
| } |
| } |
| |
| /* |
| * 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_page_list(&clean_pages, zone->zone_pgdat, &sc, |
| &stat, true); |
| memalloc_noreclaim_restore(noreclaim_flag); |
| |
| list_splice(&clean_pages, page_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]); |
| } |
| |
| } |
| |
| /* |
| * 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_pages(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(pages_skipped); |
| |
| total_scan = 0; |
| scan = 0; |
| while (scan < nr_to_scan && !list_empty(src)) { |
| struct list_head *move_to = src; |
| struct page *page; |
| |
| page = lru_to_page(src); |
| prefetchw_prev_lru_page(page, src, flags); |
| |
| nr_pages = compound_nr(page); |
| total_scan += nr_pages; |
| |
| if (page_zonenum(page) > sc->reclaim_idx) { |
| nr_skipped[page_zonenum(page)] += nr_pages; |
| move_to = &pages_skipped; |
| goto move; |
| } |
| |
| /* |
| * Do not count skipped pages because that makes the function |
| * return with no isolated pages if the LRU mostly contains |
| * ineligible pages. This causes the VM to not reclaim any |
| * pages, triggering a premature OOM. |
| * Account all tail pages of THP. |
| */ |
| scan += nr_pages; |
| |
| if (!PageLRU(page)) |
| goto move; |
| if (!sc->may_unmap && page_mapped(page)) |
| goto move; |
| |
| /* |
| * Be careful not to clear PageLRU until after we're |
| * sure the page is not being freed elsewhere -- the |
| * page release code relies on it. |
| */ |
| if (unlikely(!get_page_unless_zero(page))) |
| goto move; |
| |
| if (!TestClearPageLRU(page)) { |
| /* Another thread is already isolating this page */ |
| put_page(page); |
| goto move; |
| } |
| |
| nr_taken += nr_pages; |
| nr_zone_taken[page_zonenum(page)] += nr_pages; |
| move_to = dst; |
| move: |
| list_move(&page->lru, move_to); |
| } |
| |
| /* |
| * Splice any skipped pages 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 pages to skip and waste lots |
| * of cpu cycles. |
| */ |
| if (!list_empty(&pages_skipped)) { |
| int zid; |
| |
| list_splice(&pages_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, |
| sc->may_unmap ? 0 : ISOLATE_UNMAPPED, 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 page. This is a |
| * fundamental difference from isolate_lru_pages() (which is called |
| * without a stable reference). |
| * (2) The lru_lock must not be held. |
| * (3) Interrupts must be enabled. |
| * |
| * Return: 0 if the folio was removed from an LRU list. |
| * -EBUSY if the folio was not on an LRU list. |
| */ |
| int folio_isolate_lru(struct folio *folio) |
| { |
| int ret = -EBUSY; |
| |
| 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 = 0; |
| } |
| |
| 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 int 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 0; |
| |
| if (!writeback_throttling_sane(sc)) |
| return 0; |
| |
| 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 ((sc->gfp_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS)) |
| 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_pages_to_lru() moves pages from private @list to appropriate LRU list. |
| * On return, @list is reused as a list of pages to be freed by the caller. |
| * |
| * Returns the number of pages moved to the given lruvec. |
| */ |
| static unsigned int move_pages_to_lru(struct lruvec *lruvec, |
| struct list_head *list) |
| { |
| int nr_pages, nr_moved = 0; |
| LIST_HEAD(pages_to_free); |
| struct page *page; |
| |
| while (!list_empty(list)) { |
| page = lru_to_page(list); |
| VM_BUG_ON_PAGE(PageLRU(page), page); |
| list_del(&page->lru); |
| if (unlikely(!page_evictable(page))) { |
| spin_unlock_irq(&lruvec->lru_lock); |
| putback_lru_page(page); |
| spin_lock_irq(&lruvec->lru_lock); |
| continue; |
| } |
| |
| /* |
| * The SetPageLRU needs to be kept here for list integrity. |
| * Otherwise: |
| * #0 move_pages_to_lru #1 release_pages |
| * if !put_page_testzero |
| * if (put_page_testzero()) |
| * !PageLRU //skip lru_lock |
| * SetPageLRU() |
| * list_add(&page->lru,) |
| * list_add(&page->lru,) |
| */ |
| SetPageLRU(page); |
| |
| if (unlikely(put_page_testzero(page))) { |
| __clear_page_lru_flags(page); |
| |
| if (unlikely(PageCompound(page))) { |
| spin_unlock_irq(&lruvec->lru_lock); |
| destroy_compound_page(page); |
| spin_lock_irq(&lruvec->lru_lock); |
| } else |
| list_add(&page->lru, &pages_to_free); |
| |
| continue; |
| } |
| |
| /* |
| * All pages were isolated from the same lruvec (and isolation |
| * inhibits memcg migration). |
| */ |
| VM_BUG_ON_PAGE(!folio_matches_lruvec(page_folio(page), lruvec), page); |
| add_page_to_lru_list(page, lruvec); |
| nr_pages = thp_nr_pages(page); |
| nr_moved += nr_pages; |
| if (PageActive(page)) |
| workingset_age_nonresident(lruvec, nr_pages); |
| } |
| |
| /* |
| * To save our caller's stack, now use input list for pages to free. |
| */ |
| list_splice(&pages_to_free, list); |
| |
| 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(page_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_pages(nr_to_scan, lruvec, &page_list, |
| &nr_scanned, sc, lru); |
| |
| __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken); |
| item = current_is_kswapd() ? PGSCAN_KSWAPD : PGSCAN_DIRECT; |
| 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_page_list(&page_list, pgdat, sc, &stat, false); |
| |
| spin_lock_irq(&lruvec->lru_lock); |
| move_pages_to_lru(lruvec, &page_list); |
| |
| __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); |
| item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT; |
| 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); |
| mem_cgroup_uncharge_list(&page_list); |
| free_unref_page_list(&page_list); |
| |
| /* |
| * If dirty pages 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 pages 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 pages 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); |
| |
| 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 pages from the active LRU to the inactive LRU. |
| * |
| * We move them the other way if the page is referenced by one or more |
| * processes. |
| * |
| * If the pages are mostly unmapped, the processing is fast and it is |
| * appropriate to hold lru_lock across the whole operation. But if |
| * the pages are mapped, the processing is slow (folio_referenced()), so |
| * we should drop lru_lock around each page. It's impossible to balance |
| * this, so instead we remove the pages from the LRU while processing them. |
| * It is safe to rely on PG_active against the non-LRU pages in here because |
| * nobody will play with that bit on a non-LRU page. |
| * |
| * The downside is that we have to touch page->_refcount against each page. |
| * But we had to alter page->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 pages which were snipped off */ |
| LIST_HEAD(l_active); |
| LIST_HEAD(l_inactive); |
| unsigned nr_deactivate, nr_activate; |
| unsigned nr_rotated = 0; |
| int 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_pages(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; |
| struct page *page; |
| |
| cond_resched(); |
| folio = lru_to_folio(&l_hold); |
| list_del(&folio->lru); |
| page = &folio->page; |
| |
| if (unlikely(!page_evictable(page))) { |
| putback_lru_page(page); |
| continue; |
| } |
| |
| if (unlikely(buffer_heads_over_limit)) { |
| if (page_has_private(page) && trylock_page(page)) { |
| if (page_has_private(page)) |
| try_to_release_page(page, 0); |
| unlock_page(page); |
| } |
| } |
| |
| /* Referenced or rmap lock contention: rotate */ |
| if (folio_referenced(folio, 0, sc->target_mem_cgroup, |
| &vm_flags) != 0) { |
| /* |
| * Identify referenced, file-backed active pages 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 pages |
| * are not likely to be evicted by use-once streaming |
| * IO, plus JVM can create lots of anon VM_EXEC pages, |
| * so we ignore them here. |
| */ |
| if ((vm_flags & VM_EXEC) && page_is_file_lru(page)) { |
| nr_rotated += thp_nr_pages(page); |
| list_add(&page->lru, &l_active); |
| continue; |
| } |
| } |
| |
| ClearPageActive(page); /* we are de-activating */ |
| SetPageWorkingset(page); |
| list_add(&page->lru, &l_inactive); |
| } |
| |
| /* |
| * Move pages back to the lru list. |
| */ |
| spin_lock_irq(&lruvec->lru_lock); |
| |
| nr_activate = move_pages_to_lru(lruvec, &l_active); |
| nr_deactivate = move_pages_to_lru(lruvec, &l_inactive); |
| /* Keep all free pages in l_active list */ |
| list_splice(&l_inactive, &l_active); |
| |
| __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); |
| |
| mem_cgroup_uncharge_list(&l_active); |
| free_unref_page_list(&l_active); |
| trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate, |
| nr_deactivate, nr_rotated, sc->priority, file); |
| } |
| |
| static unsigned int reclaim_page_list(struct list_head *page_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_page_list(page_list, pgdat, &sc, &dummy_stat, false); |
| while (!list_empty(page_list)) { |
| folio = lru_to_folio(page_list); |
| list_del(&folio->lru); |
| folio_putback_lru(folio); |
| } |
| |
| return nr_reclaimed; |
| } |
| |
| unsigned long reclaim_pages(struct list_head *page_list) |
| { |
| int nid; |
| unsigned int nr_reclaimed = 0; |
| LIST_HEAD(node_page_list); |
| struct page *page; |
| unsigned int noreclaim_flag; |
| |
| if (list_empty(page_list)) |
| return nr_reclaimed; |
| |
| noreclaim_flag = memalloc_noreclaim_save(); |
| |
| nid = page_to_nid(lru_to_page(page_list)); |
| do { |
| page = lru_to_page(page_list); |
| |
| if (nid == page_to_nid(page)) { |
| ClearPageActive(page); |
| list_move(&page->lru, &node_page_list); |
| continue; |
| } |
| |
| nr_reclaimed += reclaim_page_list(&node_page_list, NODE_DATA(nid)); |
| nid = page_to_nid(lru_to_page(page_list)); |
| } while (!list_empty(page_list)); |
| |
| nr_reclaimed += reclaim_page_list(&node_page_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 |
| * page 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 pages |
| * on this LRU, maintained by the pageout code. An inactive_ratio |
| * of 3 means 3:1 or 25% of the pages 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, |
| }; |
| |
| /* |
| * Determine how aggressively the anon and file LRU lists should be |
| * scanned. |
| * |
| * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan |
| * nr[2] = file inactive pages to scan; nr[3] = file active pages 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 = mem_cgroup_swappiness(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 pages. */ |
| 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 = (200 - swappiness) * (total_cost + 1); |
| fp /= file_cost + 1; |
| |
| fraction[0] = ap; |
| fraction[1] = fp; |
| denominator = ap + fp; |
| out: |
| for_each_evictable_lru(lru) { |
| int 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); |
| } |
| |
| static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) |
| { |
| unsigned long nr[NR_LRU_LISTS]; |
| unsigned long targets[NR_LRU_LISTS]; |
| unsigned long nr_to_scan; |
| enum lru_list lru; |
| unsigned long nr_reclaimed = 0; |
| unsigned long nr_to_reclaim = sc->nr_to_reclaim; |
| struct blk_plug plug; |
| bool scan_adjusted; |
| |
| get_scan_count(lruvec, sc, nr); |
| |
| /* Record the original scan target for proportional adjustments later */ |
| memcpy(targets, nr, sizeof(nr)); |
| |
| /* |
| * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal |
| * event that can occur when there is little memory pressure e.g. |
| * multiple streaming readers/writers. Hence, we do not abort scanning |
| * when the requested number of pages are reclaimed when scanning at |
| * DEF_PRIORITY on the assumption that the fact we are direct |
| * reclaiming implies that kswapd is not keeping up and it is best to |
| * do a batch of work at once. For memcg reclaim one check is made to |
| * abort proportional reclaim if either the file or anon lru has already |
| * dropped to zero at the first pass. |
| */ |
| scan_adjusted = (!cgroup_reclaim(sc) && !current_is_kswapd() && |
| sc->priority == DEF_PRIORITY); |
| |
| blk_start_plug(&plug); |
| while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
| nr[LRU_INACTIVE_FILE]) { |
| unsigned long nr_anon, nr_file, percentage; |
| unsigned long nr_scanned; |
| |
| for_each_evictable_lru(lru) { |
| if (nr[lru]) { |
| nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX); |
| nr[lru] -= nr_to_scan; |
| |
| nr_reclaimed += shrink_list(lru, nr_to_scan, |
| lruvec, sc); |
| } |
| } |
| |
| cond_resched(); |
| |
| if (nr_reclaimed < nr_to_reclaim || scan_adjusted) |
| continue; |
| |
| /* |
| * For kswapd and memcg, reclaim at least the number of pages |
| * requested. Ensure that the anon and file LRUs are scanned |
| * proportionally what was requested by get_scan_count(). We |
| * stop reclaiming one LRU and reduce the amount scanning |
| * proportional to the original scan target. |
| */ |
| nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; |
| nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; |
| |
| /* |
| * It's just vindictive to attack the larger once the smaller |
| * has gone to zero. And given the way we stop scanning the |
| * smaller below, this makes sure that we only make one nudge |
| * towards proportionality once we've got nr_to_reclaim. |
| */ |
| if (!nr_file || !nr_anon) |
| break; |
| |
| if (nr_file > nr_anon) { |
| unsigned long scan_target = targets[LRU_INACTIVE_ANON] + |
| targets[LRU_ACTIVE_ANON] + 1; |
| lru = LRU_BASE; |
| percentage = nr_anon * 100 / scan_target; |
| } else { |
| unsigned long scan_target = targets[LRU_INACTIVE_FILE] + |
| targets[LRU_ACTIVE_FILE] + 1; |
| lru = LRU_FILE; |
| percentage = nr_file * 100 / scan_target; |
| } |
| |
| /* Stop scanning the smaller of the LRU */ |
| nr[lru] = 0; |
| nr[lru + LRU_ACTIVE] = 0; |
| |
| /* |
| * Recalculate the other LRU scan count based on its original |
| * scan target and the percentage scanning already complete |
| */ |
| lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; |
| nr_scanned = targets[lru] - nr[lru]; |
| nr[lru] = targets[lru] * (100 - percentage) / 100; |
| nr[lru] -= min(nr[lru], nr_scanned); |
| |
| lru += LRU_ACTIVE; |
| nr_scanned = targets[lru] - nr[lru]; |
| nr[lru] = targets[lru] * (100 - percentage) / 100; |
| nr[lru] -= min(nr[lru], nr_scanned); |
| |
| scan_adjusted = true; |
| } |
| blk_finish_plug(&plug); |
| sc->nr_reclaimed += nr_reclaimed; |
| |
| /* |
| * Even if we did not try to evict anon pages at all, we want to |
| * rebalance the anon lru active/inactive ratio. |
| */ |
| if (can_age_anon_pages(lruvec_pgdat(lruvec), sc) && |
| inactive_is_low(lruvec, LRU_INACTIVE_ANON)) |
| shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
| sc, LRU_ACTIVE_ANON); |
| } |
| |
| /* Use reclaim/compaction for costly allocs or under memory pressure */ |
| static bool in_reclaim_compaction(struct scan_control *sc) |
| { |
| if (IS_ENABLED(CONFIG_COMPACTION) && sc->order && |
| (sc->order > PAGE_ALLOC_COSTLY_ORDER || |
| sc->priority < DEF_PRIORITY - 2)) |
| return true; |
| |
| return false; |
| } |
| |
| /* |
| * Reclaim/compaction is used for high-order allocation requests. It reclaims |
| * order-0 pages before compacting the zone. should_continue_reclaim() returns |
| * true if more pages should be reclaimed such that when the page allocator |
| * calls try_to_compact_pages() that it will have enough free pages to succeed. |
| * It will give up earlier than that if there is difficulty reclaiming pages. |
| */ |
| static inline bool should_continue_reclaim(struct pglist_data *pgdat, |
| unsigned long nr_reclaimed, |
| struct scan_control *sc) |
| { |
| unsigned long pages_for_compaction; |
| unsigned long inactive_lru_pages; |
| int z; |
| |
| /* If not in reclaim/compaction mode, stop */ |
| if (!in_reclaim_compaction(sc)) |
| return false; |
| |
| /* |
| * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX |
| * number of pages that were scanned. This will return to the caller |
| * with the risk reclaim/compaction and the resulting allocation attempt |
| * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL |
| * allocations through requiring that the full LRU list has been scanned |
| * first, by assuming that zero delta of sc->nr_scanned means full LRU |
| * scan, but that approximation was wrong, and there were corner cases |
| * where always a non-zero amount of pages were scanned. |
| */ |
| if (!nr_reclaimed) |
| return false; |
| |
| /* If compaction would go ahead or the allocation would succeed, stop */ |
| for (z = 0; z <= sc->reclaim_idx; z++) { |
| struct zone *zone = &pgdat->node_zones[z]; |
| if (!managed_zone(zone)) |
| continue; |
| |
| switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) { |
| case COMPACT_SUCCESS: |
| case COMPACT_CONTINUE: |
| return false; |
| default: |
| /* check next zone */ |
| ; |
| } |
| } |
| |
| /* |
| * If we have not reclaimed enough pages for compaction and the |
| * inactive lists are large enough, continue reclaiming |
| */ |
| pages_for_compaction = compact_gap(sc->order); |
| inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); |
| if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc)) |
| inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); |
| |
| return inactive_lru_pages > pages_for_compaction; |
| } |
| |
| static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) |
| { |
| struct mem_cgroup *target_memcg = sc->target_mem_cgroup; |
| struct mem_cgroup *memcg; |
| |
| memcg = mem_cgroup_iter(target_memcg, NULL, NULL); |
| do { |
| struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); |
| unsigned long reclaimed; |
| unsigned long scanned; |
| |
| /* |
| * This loop can become CPU-bound when target memcgs |
| * aren't eligible for reclaim - either because they |
| * don't have any reclaimable pages, or because their |
| * memory is explicitly protected. Avoid soft lockups. |
| */ |
| cond_resched(); |
| |
| mem_cgroup_calculate_protection(target_memcg, memcg); |
| |
| if (mem_cgroup_below_min(memcg)) { |
| /* |
| * Hard protection. |
| * If there is no reclaimable memory, OOM. |
| */ |
| continue; |
| } else if (mem_cgroup_below_low(memcg)) { |
| /* |
| * Soft protection. |
| * Respect the protection only as long as |
| * there is an unprotected supply |
| * of reclaimable memory from other cgroups. |
| */ |
| if (!sc->memcg_low_reclaim) { |
| sc->memcg_low_skipped = 1; |
| continue; |
| } |
| memcg_memory_event(memcg, MEMCG_LOW); |
| } |
| |
| reclaimed = sc->nr_reclaimed; |
| scanned = sc->nr_scanned; |
| |
| shrink_lruvec(lruvec, sc); |
| |
| shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, |
| sc->priority); |
| |
| /* Record the group's reclaim efficiency */ |
| vmpressure(sc->gfp_mask, memcg, false, |
| sc->nr_scanned - scanned, |
| sc->nr_reclaimed - reclaimed); |
| |
| } while ((memcg = mem_cgroup_iter(target_memcg, memcg, NULL))); |
| } |
| |
| static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) |
| { |
| struct reclaim_state *reclaim_state = current->reclaim_state; |
| unsigned long nr_reclaimed, nr_scanned; |
| struct lruvec *target_lruvec; |
| bool reclaimable = false; |
| unsigned long file; |
| |
| target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); |
| |
| again: |
| /* |
| * Flush the memory cgroup stats, so that we read accurate per-memcg |
| * lruvec stats for heuristics. |
| */ |
| mem_cgroup_flush_stats(); |
| |
| memset(&sc->nr, 0, sizeof(sc->nr)); |
| |
| nr_reclaimed = sc->nr_reclaimed; |
| nr_scanned = sc->nr_scanned; |
| |
| /* |
| * 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; |
| |
| refaults = lruvec_page_state(target_lruvec, |
| WORKINGSET_ACTIVATE_ANON); |
| if (refaults != target_lruvec->refaults[0] || |
| inactive_is_low(target_lruvec, LRU_INACTIVE_ANON)) |
| sc->may_deactivate |= DEACTIVATE_ANON; |
| else |
| sc->may_deactivate &= ~DEACTIVATE_ANON; |
| |
| /* |
| * 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_FILE); |
| if (refaults != target_lruvec->refaults[1] || |
| 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->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; |
| } |
| |
| shrink_node_memcgs(pgdat, sc); |
| |
| if (reclaim_state) { |
| sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
| reclaim_state->reclaimed_slab = 0; |
| } |
| |
| /* Record the subtree's reclaim efficiency */ |
| vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, |
| sc->nr_scanned - nr_scanned, |
| sc->nr_reclaimed - nr_reclaimed); |
| |
| if (sc->nr_reclaimed - nr_reclaimed) |
| reclaimable = true; |
| |
| if (current_is_kswapd()) { |
| /* |
| * If reclaim is isolating dirty pages under writeback, |
| * it implies that the long-lived page allocation rate |
| * is exceeding the page laundering rate. Either the |
| * global limits are not being effective at throttling |
| * processes due to the page distribution throughout |
| * zones or there is heavy usage of a slow backing |
| * device. The only option is to throttle from reclaim |
| * context which is not ideal as there is no guarantee |
| * the dirtying process is throttled in the same way |
| * balance_dirty_pages() manages. |
| * |
| * Once a node is flagged PGDAT_WRITEBACK, kswapd will |
| * count the number of pages under pages flagged for |
| * immediate reclaim and stall if any are encountered |
| * in the nr_immediate check below. |
| */ |
| if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken) |
| set_bit(PGDAT_WRITEBACK, &pgdat->flags); |
| |
| /* Allow kswapd to start writing pages during reclaim.*/ |
| if (sc->nr.unqueued_dirty == sc->nr.file_taken) |
| set_bit(PGDAT_DIRTY, &pgdat->flags); |
| |
| /* |
| * If kswapd scans pages marked for immediate |
| * reclaim and under writeback (nr_immediate), it |
| * implies that pages are cycling through the LRU |
| * faster than they are written so forcibly stall |
| * until some pages complete writeback. |
| */ |
| if (sc->nr.immediate) |
| reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK); |
| } |
| |
| /* |
| * Tag a node/memcg as congested if all the dirty pages were marked |
| * for writeback and immediate reclaim (counted in nr.congested). |
| * |
| * Legacy memcg will stall in page writeback so avoid forcibly |
| * stalling in reclaim_throttle(). |
| */ |
| if ((current_is_kswapd() || |
| (cgroup_reclaim(sc) && writeback_throttling_sane(sc))) && |
| sc->nr.dirty && sc->nr.dirty == sc->nr.congested) |
| set_bit(LRUVEC_CONGESTED, &target_lruvec->flags); |
| |
| /* |
| * Stall direct reclaim for IO completions if the lruvec is |
| * node is congested. Allow kswapd to continue until it |
| * starts encountering unqueued dirty pages or cycling through |
| * the LRU too quickly. |
| */ |
| if (!current_is_kswapd() && current_may_throttle() && |
| !sc->hibernation_mode && |
| test_bit(LRUVEC_CONGESTED, &target_lruvec->flags)) |
|