| /* SPDX-License-Identifier: GPL-2.0 |
| * |
| * IO cost model based controller. |
| * |
| * Copyright (C) 2019 Tejun Heo <tj@kernel.org> |
| * Copyright (C) 2019 Andy Newell <newella@fb.com> |
| * Copyright (C) 2019 Facebook |
| * |
| * One challenge of controlling IO resources is the lack of trivially |
| * observable cost metric. This is distinguished from CPU and memory where |
| * wallclock time and the number of bytes can serve as accurate enough |
| * approximations. |
| * |
| * Bandwidth and iops are the most commonly used metrics for IO devices but |
| * depending on the type and specifics of the device, different IO patterns |
| * easily lead to multiple orders of magnitude variations rendering them |
| * useless for the purpose of IO capacity distribution. While on-device |
| * time, with a lot of clutches, could serve as a useful approximation for |
| * non-queued rotational devices, this is no longer viable with modern |
| * devices, even the rotational ones. |
| * |
| * While there is no cost metric we can trivially observe, it isn't a |
| * complete mystery. For example, on a rotational device, seek cost |
| * dominates while a contiguous transfer contributes a smaller amount |
| * proportional to the size. If we can characterize at least the relative |
| * costs of these different types of IOs, it should be possible to |
| * implement a reasonable work-conserving proportional IO resource |
| * distribution. |
| * |
| * 1. IO Cost Model |
| * |
| * IO cost model estimates the cost of an IO given its basic parameters and |
| * history (e.g. the end sector of the last IO). The cost is measured in |
| * device time. If a given IO is estimated to cost 10ms, the device should |
| * be able to process ~100 of those IOs in a second. |
| * |
| * Currently, there's only one builtin cost model - linear. Each IO is |
| * classified as sequential or random and given a base cost accordingly. |
| * On top of that, a size cost proportional to the length of the IO is |
| * added. While simple, this model captures the operational |
| * characteristics of a wide varienty of devices well enough. Default |
| * parameters for several different classes of devices are provided and the |
| * parameters can be configured from userspace via |
| * /sys/fs/cgroup/io.cost.model. |
| * |
| * If needed, tools/cgroup/iocost_coef_gen.py can be used to generate |
| * device-specific coefficients. |
| * |
| * 2. Control Strategy |
| * |
| * The device virtual time (vtime) is used as the primary control metric. |
| * The control strategy is composed of the following three parts. |
| * |
| * 2-1. Vtime Distribution |
| * |
| * When a cgroup becomes active in terms of IOs, its hierarchical share is |
| * calculated. Please consider the following hierarchy where the numbers |
| * inside parentheses denote the configured weights. |
| * |
| * root |
| * / \ |
| * A (w:100) B (w:300) |
| * / \ |
| * A0 (w:100) A1 (w:100) |
| * |
| * If B is idle and only A0 and A1 are actively issuing IOs, as the two are |
| * of equal weight, each gets 50% share. If then B starts issuing IOs, B |
| * gets 300/(100+300) or 75% share, and A0 and A1 equally splits the rest, |
| * 12.5% each. The distribution mechanism only cares about these flattened |
| * shares. They're called hweights (hierarchical weights) and always add |
| * upto 1 (WEIGHT_ONE). |
| * |
| * A given cgroup's vtime runs slower in inverse proportion to its hweight. |
| * For example, with 12.5% weight, A0's time runs 8 times slower (100/12.5) |
| * against the device vtime - an IO which takes 10ms on the underlying |
| * device is considered to take 80ms on A0. |
| * |
| * This constitutes the basis of IO capacity distribution. Each cgroup's |
| * vtime is running at a rate determined by its hweight. A cgroup tracks |
| * the vtime consumed by past IOs and can issue a new IO if doing so |
| * wouldn't outrun the current device vtime. Otherwise, the IO is |
| * suspended until the vtime has progressed enough to cover it. |
| * |
| * 2-2. Vrate Adjustment |
| * |
| * It's unrealistic to expect the cost model to be perfect. There are too |
| * many devices and even on the same device the overall performance |
| * fluctuates depending on numerous factors such as IO mixture and device |
| * internal garbage collection. The controller needs to adapt dynamically. |
| * |
| * This is achieved by adjusting the overall IO rate according to how busy |
| * the device is. If the device becomes overloaded, we're sending down too |
| * many IOs and should generally slow down. If there are waiting issuers |
| * but the device isn't saturated, we're issuing too few and should |
| * generally speed up. |
| * |
| * To slow down, we lower the vrate - the rate at which the device vtime |
| * passes compared to the wall clock. For example, if the vtime is running |
| * at the vrate of 75%, all cgroups added up would only be able to issue |
| * 750ms worth of IOs per second, and vice-versa for speeding up. |
| * |
| * Device business is determined using two criteria - rq wait and |
| * completion latencies. |
| * |
| * When a device gets saturated, the on-device and then the request queues |
| * fill up and a bio which is ready to be issued has to wait for a request |
| * to become available. When this delay becomes noticeable, it's a clear |
| * indication that the device is saturated and we lower the vrate. This |
| * saturation signal is fairly conservative as it only triggers when both |
| * hardware and software queues are filled up, and is used as the default |
| * busy signal. |
| * |
| * As devices can have deep queues and be unfair in how the queued commands |
| * are executed, solely depending on rq wait may not result in satisfactory |
| * control quality. For a better control quality, completion latency QoS |
| * parameters can be configured so that the device is considered saturated |
| * if N'th percentile completion latency rises above the set point. |
| * |
| * The completion latency requirements are a function of both the |
| * underlying device characteristics and the desired IO latency quality of |
| * service. There is an inherent trade-off - the tighter the latency QoS, |
| * the higher the bandwidth lossage. Latency QoS is disabled by default |
| * and can be set through /sys/fs/cgroup/io.cost.qos. |
| * |
| * 2-3. Work Conservation |
| * |
| * Imagine two cgroups A and B with equal weights. A is issuing a small IO |
| * periodically while B is sending out enough parallel IOs to saturate the |
| * device on its own. Let's say A's usage amounts to 100ms worth of IO |
| * cost per second, i.e., 10% of the device capacity. The naive |
| * distribution of half and half would lead to 60% utilization of the |
| * device, a significant reduction in the total amount of work done |
| * compared to free-for-all competition. This is too high a cost to pay |
| * for IO control. |
| * |
| * To conserve the total amount of work done, we keep track of how much |
| * each active cgroup is actually using and yield part of its weight if |
| * there are other cgroups which can make use of it. In the above case, |
| * A's weight will be lowered so that it hovers above the actual usage and |
| * B would be able to use the rest. |
| * |
| * As we don't want to penalize a cgroup for donating its weight, the |
| * surplus weight adjustment factors in a margin and has an immediate |
| * snapback mechanism in case the cgroup needs more IO vtime for itself. |
| * |
| * Note that adjusting down surplus weights has the same effects as |
| * accelerating vtime for other cgroups and work conservation can also be |
| * implemented by adjusting vrate dynamically. However, squaring who can |
| * donate and should take back how much requires hweight propagations |
| * anyway making it easier to implement and understand as a separate |
| * mechanism. |
| * |
| * 3. Monitoring |
| * |
| * Instead of debugfs or other clumsy monitoring mechanisms, this |
| * controller uses a drgn based monitoring script - |
| * tools/cgroup/iocost_monitor.py. For details on drgn, please see |
| * https://github.com/osandov/drgn. The output looks like the following. |
| * |
| * sdb RUN per=300ms cur_per=234.218:v203.695 busy= +1 vrate= 62.12% |
| * active weight hweight% inflt% dbt delay usages% |
| * test/a * 50/ 50 33.33/ 33.33 27.65 2 0*041 033:033:033 |
| * test/b * 100/ 100 66.67/ 66.67 17.56 0 0*000 066:079:077 |
| * |
| * - per : Timer period |
| * - cur_per : Internal wall and device vtime clock |
| * - vrate : Device virtual time rate against wall clock |
| * - weight : Surplus-adjusted and configured weights |
| * - hweight : Surplus-adjusted and configured hierarchical weights |
| * - inflt : The percentage of in-flight IO cost at the end of last period |
| * - del_ms : Deferred issuer delay induction level and duration |
| * - usages : Usage history |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/module.h> |
| #include <linux/timer.h> |
| #include <linux/time64.h> |
| #include <linux/parser.h> |
| #include <linux/sched/signal.h> |
| #include <asm/local.h> |
| #include <asm/local64.h> |
| #include "blk-rq-qos.h" |
| #include "blk-stat.h" |
| #include "blk-wbt.h" |
| #include "blk-cgroup.h" |
| |
| #ifdef CONFIG_TRACEPOINTS |
| |
| /* copied from TRACE_CGROUP_PATH, see cgroup-internal.h */ |
| #define TRACE_IOCG_PATH_LEN 1024 |
| static DEFINE_SPINLOCK(trace_iocg_path_lock); |
| static char trace_iocg_path[TRACE_IOCG_PATH_LEN]; |
| |
| #define TRACE_IOCG_PATH(type, iocg, ...) \ |
| do { \ |
| unsigned long flags; \ |
| if (trace_iocost_##type##_enabled()) { \ |
| spin_lock_irqsave(&trace_iocg_path_lock, flags); \ |
| cgroup_path(iocg_to_blkg(iocg)->blkcg->css.cgroup, \ |
| trace_iocg_path, TRACE_IOCG_PATH_LEN); \ |
| trace_iocost_##type(iocg, trace_iocg_path, \ |
| ##__VA_ARGS__); \ |
| spin_unlock_irqrestore(&trace_iocg_path_lock, flags); \ |
| } \ |
| } while (0) |
| |
| #else /* CONFIG_TRACE_POINTS */ |
| #define TRACE_IOCG_PATH(type, iocg, ...) do { } while (0) |
| #endif /* CONFIG_TRACE_POINTS */ |
| |
| enum { |
| MILLION = 1000000, |
| |
| /* timer period is calculated from latency requirements, bound it */ |
| MIN_PERIOD = USEC_PER_MSEC, |
| MAX_PERIOD = USEC_PER_SEC, |
| |
| /* |
| * iocg->vtime is targeted at 50% behind the device vtime, which |
| * serves as its IO credit buffer. Surplus weight adjustment is |
| * immediately canceled if the vtime margin runs below 10%. |
| */ |
| MARGIN_MIN_PCT = 10, |
| MARGIN_LOW_PCT = 20, |
| MARGIN_TARGET_PCT = 50, |
| |
| INUSE_ADJ_STEP_PCT = 25, |
| |
| /* Have some play in timer operations */ |
| TIMER_SLACK_PCT = 1, |
| |
| /* 1/64k is granular enough and can easily be handled w/ u32 */ |
| WEIGHT_ONE = 1 << 16, |
| }; |
| |
| enum { |
| /* |
| * As vtime is used to calculate the cost of each IO, it needs to |
| * be fairly high precision. For example, it should be able to |
| * represent the cost of a single page worth of discard with |
| * suffificient accuracy. At the same time, it should be able to |
| * represent reasonably long enough durations to be useful and |
| * convenient during operation. |
| * |
| * 1s worth of vtime is 2^37. This gives us both sub-nanosecond |
| * granularity and days of wrap-around time even at extreme vrates. |
| */ |
| VTIME_PER_SEC_SHIFT = 37, |
| VTIME_PER_SEC = 1LLU << VTIME_PER_SEC_SHIFT, |
| VTIME_PER_USEC = VTIME_PER_SEC / USEC_PER_SEC, |
| VTIME_PER_NSEC = VTIME_PER_SEC / NSEC_PER_SEC, |
| |
| /* bound vrate adjustments within two orders of magnitude */ |
| VRATE_MIN_PPM = 10000, /* 1% */ |
| VRATE_MAX_PPM = 100000000, /* 10000% */ |
| |
| VRATE_MIN = VTIME_PER_USEC * VRATE_MIN_PPM / MILLION, |
| VRATE_CLAMP_ADJ_PCT = 4, |
| |
| /* switch iff the conditions are met for longer than this */ |
| AUTOP_CYCLE_NSEC = 10LLU * NSEC_PER_SEC, |
| }; |
| |
| enum { |
| /* if IOs end up waiting for requests, issue less */ |
| RQ_WAIT_BUSY_PCT = 5, |
| |
| /* unbusy hysterisis */ |
| UNBUSY_THR_PCT = 75, |
| |
| /* |
| * The effect of delay is indirect and non-linear and a huge amount of |
| * future debt can accumulate abruptly while unthrottled. Linearly scale |
| * up delay as debt is going up and then let it decay exponentially. |
| * This gives us quick ramp ups while delay is accumulating and long |
| * tails which can help reducing the frequency of debt explosions on |
| * unthrottle. The parameters are experimentally determined. |
| * |
| * The delay mechanism provides adequate protection and behavior in many |
| * cases. However, this is far from ideal and falls shorts on both |
| * fronts. The debtors are often throttled too harshly costing a |
| * significant level of fairness and possibly total work while the |
| * protection against their impacts on the system can be choppy and |
| * unreliable. |
| * |
| * The shortcoming primarily stems from the fact that, unlike for page |
| * cache, the kernel doesn't have well-defined back-pressure propagation |
| * mechanism and policies for anonymous memory. Fully addressing this |
| * issue will likely require substantial improvements in the area. |
| */ |
| MIN_DELAY_THR_PCT = 500, |
| MAX_DELAY_THR_PCT = 25000, |
| MIN_DELAY = 250, |
| MAX_DELAY = 250 * USEC_PER_MSEC, |
| |
| /* halve debts if avg usage over 100ms is under 50% */ |
| DFGV_USAGE_PCT = 50, |
| DFGV_PERIOD = 100 * USEC_PER_MSEC, |
| |
| /* don't let cmds which take a very long time pin lagging for too long */ |
| MAX_LAGGING_PERIODS = 10, |
| |
| /* |
| * Count IO size in 4k pages. The 12bit shift helps keeping |
| * size-proportional components of cost calculation in closer |
| * numbers of digits to per-IO cost components. |
| */ |
| IOC_PAGE_SHIFT = 12, |
| IOC_PAGE_SIZE = 1 << IOC_PAGE_SHIFT, |
| IOC_SECT_TO_PAGE_SHIFT = IOC_PAGE_SHIFT - SECTOR_SHIFT, |
| |
| /* if apart further than 16M, consider randio for linear model */ |
| LCOEF_RANDIO_PAGES = 4096, |
| }; |
| |
| enum ioc_running { |
| IOC_IDLE, |
| IOC_RUNNING, |
| IOC_STOP, |
| }; |
| |
| /* io.cost.qos controls including per-dev enable of the whole controller */ |
| enum { |
| QOS_ENABLE, |
| QOS_CTRL, |
| NR_QOS_CTRL_PARAMS, |
| }; |
| |
| /* io.cost.qos params */ |
| enum { |
| QOS_RPPM, |
| QOS_RLAT, |
| QOS_WPPM, |
| QOS_WLAT, |
| QOS_MIN, |
| QOS_MAX, |
| NR_QOS_PARAMS, |
| }; |
| |
| /* io.cost.model controls */ |
| enum { |
| COST_CTRL, |
| COST_MODEL, |
| NR_COST_CTRL_PARAMS, |
| }; |
| |
| /* builtin linear cost model coefficients */ |
| enum { |
| I_LCOEF_RBPS, |
| I_LCOEF_RSEQIOPS, |
| I_LCOEF_RRANDIOPS, |
| I_LCOEF_WBPS, |
| I_LCOEF_WSEQIOPS, |
| I_LCOEF_WRANDIOPS, |
| NR_I_LCOEFS, |
| }; |
| |
| enum { |
| LCOEF_RPAGE, |
| LCOEF_RSEQIO, |
| LCOEF_RRANDIO, |
| LCOEF_WPAGE, |
| LCOEF_WSEQIO, |
| LCOEF_WRANDIO, |
| NR_LCOEFS, |
| }; |
| |
| enum { |
| AUTOP_INVALID, |
| AUTOP_HDD, |
| AUTOP_SSD_QD1, |
| AUTOP_SSD_DFL, |
| AUTOP_SSD_FAST, |
| }; |
| |
| struct ioc_params { |
| u32 qos[NR_QOS_PARAMS]; |
| u64 i_lcoefs[NR_I_LCOEFS]; |
| u64 lcoefs[NR_LCOEFS]; |
| u32 too_fast_vrate_pct; |
| u32 too_slow_vrate_pct; |
| }; |
| |
| struct ioc_margins { |
| s64 min; |
| s64 low; |
| s64 target; |
| }; |
| |
| struct ioc_missed { |
| local_t nr_met; |
| local_t nr_missed; |
| u32 last_met; |
| u32 last_missed; |
| }; |
| |
| struct ioc_pcpu_stat { |
| struct ioc_missed missed[2]; |
| |
| local64_t rq_wait_ns; |
| u64 last_rq_wait_ns; |
| }; |
| |
| /* per device */ |
| struct ioc { |
| struct rq_qos rqos; |
| |
| bool enabled; |
| |
| struct ioc_params params; |
| struct ioc_margins margins; |
| u32 period_us; |
| u32 timer_slack_ns; |
| u64 vrate_min; |
| u64 vrate_max; |
| |
| spinlock_t lock; |
| struct timer_list timer; |
| struct list_head active_iocgs; /* active cgroups */ |
| struct ioc_pcpu_stat __percpu *pcpu_stat; |
| |
| enum ioc_running running; |
| atomic64_t vtime_rate; |
| u64 vtime_base_rate; |
| s64 vtime_err; |
| |
| seqcount_spinlock_t period_seqcount; |
| u64 period_at; /* wallclock starttime */ |
| u64 period_at_vtime; /* vtime starttime */ |
| |
| atomic64_t cur_period; /* inc'd each period */ |
| int busy_level; /* saturation history */ |
| |
| bool weights_updated; |
| atomic_t hweight_gen; /* for lazy hweights */ |
| |
| /* debt forgivness */ |
| u64 dfgv_period_at; |
| u64 dfgv_period_rem; |
| u64 dfgv_usage_us_sum; |
| |
| u64 autop_too_fast_at; |
| u64 autop_too_slow_at; |
| int autop_idx; |
| bool user_qos_params:1; |
| bool user_cost_model:1; |
| }; |
| |
| struct iocg_pcpu_stat { |
| local64_t abs_vusage; |
| }; |
| |
| struct iocg_stat { |
| u64 usage_us; |
| u64 wait_us; |
| u64 indebt_us; |
| u64 indelay_us; |
| }; |
| |
| /* per device-cgroup pair */ |
| struct ioc_gq { |
| struct blkg_policy_data pd; |
| struct ioc *ioc; |
| |
| /* |
| * A iocg can get its weight from two sources - an explicit |
| * per-device-cgroup configuration or the default weight of the |
| * cgroup. `cfg_weight` is the explicit per-device-cgroup |
| * configuration. `weight` is the effective considering both |
| * sources. |
| * |
| * When an idle cgroup becomes active its `active` goes from 0 to |
| * `weight`. `inuse` is the surplus adjusted active weight. |
| * `active` and `inuse` are used to calculate `hweight_active` and |
| * `hweight_inuse`. |
| * |
| * `last_inuse` remembers `inuse` while an iocg is idle to persist |
| * surplus adjustments. |
| * |
| * `inuse` may be adjusted dynamically during period. `saved_*` are used |
| * to determine and track adjustments. |
| */ |
| u32 cfg_weight; |
| u32 weight; |
| u32 active; |
| u32 inuse; |
| |
| u32 last_inuse; |
| s64 saved_margin; |
| |
| sector_t cursor; /* to detect randio */ |
| |
| /* |
| * `vtime` is this iocg's vtime cursor which progresses as IOs are |
| * issued. If lagging behind device vtime, the delta represents |
| * the currently available IO budget. If running ahead, the |
| * overage. |
| * |
| * `vtime_done` is the same but progressed on completion rather |
| * than issue. The delta behind `vtime` represents the cost of |
| * currently in-flight IOs. |
| */ |
| atomic64_t vtime; |
| atomic64_t done_vtime; |
| u64 abs_vdebt; |
| |
| /* current delay in effect and when it started */ |
| u64 delay; |
| u64 delay_at; |
| |
| /* |
| * The period this iocg was last active in. Used for deactivation |
| * and invalidating `vtime`. |
| */ |
| atomic64_t active_period; |
| struct list_head active_list; |
| |
| /* see __propagate_weights() and current_hweight() for details */ |
| u64 child_active_sum; |
| u64 child_inuse_sum; |
| u64 child_adjusted_sum; |
| int hweight_gen; |
| u32 hweight_active; |
| u32 hweight_inuse; |
| u32 hweight_donating; |
| u32 hweight_after_donation; |
| |
| struct list_head walk_list; |
| struct list_head surplus_list; |
| |
| struct wait_queue_head waitq; |
| struct hrtimer waitq_timer; |
| |
| /* timestamp at the latest activation */ |
| u64 activated_at; |
| |
| /* statistics */ |
| struct iocg_pcpu_stat __percpu *pcpu_stat; |
| struct iocg_stat stat; |
| struct iocg_stat last_stat; |
| u64 last_stat_abs_vusage; |
| u64 usage_delta_us; |
| u64 wait_since; |
| u64 indebt_since; |
| u64 indelay_since; |
| |
| /* this iocg's depth in the hierarchy and ancestors including self */ |
| int level; |
| struct ioc_gq *ancestors[]; |
| }; |
| |
| /* per cgroup */ |
| struct ioc_cgrp { |
| struct blkcg_policy_data cpd; |
| unsigned int dfl_weight; |
| }; |
| |
| struct ioc_now { |
| u64 now_ns; |
| u64 now; |
| u64 vnow; |
| }; |
| |
| struct iocg_wait { |
| struct wait_queue_entry wait; |
| struct bio *bio; |
| u64 abs_cost; |
| bool committed; |
| }; |
| |
| struct iocg_wake_ctx { |
| struct ioc_gq *iocg; |
| u32 hw_inuse; |
| s64 vbudget; |
| }; |
| |
| static const struct ioc_params autop[] = { |
| [AUTOP_HDD] = { |
| .qos = { |
| [QOS_RLAT] = 250000, /* 250ms */ |
| [QOS_WLAT] = 250000, |
| [QOS_MIN] = VRATE_MIN_PPM, |
| [QOS_MAX] = VRATE_MAX_PPM, |
| }, |
| .i_lcoefs = { |
| [I_LCOEF_RBPS] = 174019176, |
| [I_LCOEF_RSEQIOPS] = 41708, |
| [I_LCOEF_RRANDIOPS] = 370, |
| [I_LCOEF_WBPS] = 178075866, |
| [I_LCOEF_WSEQIOPS] = 42705, |
| [I_LCOEF_WRANDIOPS] = 378, |
| }, |
| }, |
| [AUTOP_SSD_QD1] = { |
| .qos = { |
| [QOS_RLAT] = 25000, /* 25ms */ |
| [QOS_WLAT] = 25000, |
| [QOS_MIN] = VRATE_MIN_PPM, |
| [QOS_MAX] = VRATE_MAX_PPM, |
| }, |
| .i_lcoefs = { |
| [I_LCOEF_RBPS] = 245855193, |
| [I_LCOEF_RSEQIOPS] = 61575, |
| [I_LCOEF_RRANDIOPS] = 6946, |
| [I_LCOEF_WBPS] = 141365009, |
| [I_LCOEF_WSEQIOPS] = 33716, |
| [I_LCOEF_WRANDIOPS] = 26796, |
| }, |
| }, |
| [AUTOP_SSD_DFL] = { |
| .qos = { |
| [QOS_RLAT] = 25000, /* 25ms */ |
| [QOS_WLAT] = 25000, |
| [QOS_MIN] = VRATE_MIN_PPM, |
| [QOS_MAX] = VRATE_MAX_PPM, |
| }, |
| .i_lcoefs = { |
| [I_LCOEF_RBPS] = 488636629, |
| [I_LCOEF_RSEQIOPS] = 8932, |
| [I_LCOEF_RRANDIOPS] = 8518, |
| [I_LCOEF_WBPS] = 427891549, |
| [I_LCOEF_WSEQIOPS] = 28755, |
| [I_LCOEF_WRANDIOPS] = 21940, |
| }, |
| .too_fast_vrate_pct = 500, |
| }, |
| [AUTOP_SSD_FAST] = { |
| .qos = { |
| [QOS_RLAT] = 5000, /* 5ms */ |
| [QOS_WLAT] = 5000, |
| [QOS_MIN] = VRATE_MIN_PPM, |
| [QOS_MAX] = VRATE_MAX_PPM, |
| }, |
| .i_lcoefs = { |
| [I_LCOEF_RBPS] = 3102524156LLU, |
| [I_LCOEF_RSEQIOPS] = 724816, |
| [I_LCOEF_RRANDIOPS] = 778122, |
| [I_LCOEF_WBPS] = 1742780862LLU, |
| [I_LCOEF_WSEQIOPS] = 425702, |
| [I_LCOEF_WRANDIOPS] = 443193, |
| }, |
| .too_slow_vrate_pct = 10, |
| }, |
| }; |
| |
| /* |
| * vrate adjust percentages indexed by ioc->busy_level. We adjust up on |
| * vtime credit shortage and down on device saturation. |
| */ |
| static u32 vrate_adj_pct[] = |
| { 0, 0, 0, 0, |
| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, |
| 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, |
| 4, 4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16 }; |
| |
| static struct blkcg_policy blkcg_policy_iocost; |
| |
| /* accessors and helpers */ |
| static struct ioc *rqos_to_ioc(struct rq_qos *rqos) |
| { |
| return container_of(rqos, struct ioc, rqos); |
| } |
| |
| static struct ioc *q_to_ioc(struct request_queue *q) |
| { |
| return rqos_to_ioc(rq_qos_id(q, RQ_QOS_COST)); |
| } |
| |
| static const char __maybe_unused *ioc_name(struct ioc *ioc) |
| { |
| struct gendisk *disk = ioc->rqos.disk; |
| |
| if (!disk) |
| return "<unknown>"; |
| return disk->disk_name; |
| } |
| |
| static struct ioc_gq *pd_to_iocg(struct blkg_policy_data *pd) |
| { |
| return pd ? container_of(pd, struct ioc_gq, pd) : NULL; |
| } |
| |
| static struct ioc_gq *blkg_to_iocg(struct blkcg_gq *blkg) |
| { |
| return pd_to_iocg(blkg_to_pd(blkg, &blkcg_policy_iocost)); |
| } |
| |
| static struct blkcg_gq *iocg_to_blkg(struct ioc_gq *iocg) |
| { |
| return pd_to_blkg(&iocg->pd); |
| } |
| |
| static struct ioc_cgrp *blkcg_to_iocc(struct blkcg *blkcg) |
| { |
| return container_of(blkcg_to_cpd(blkcg, &blkcg_policy_iocost), |
| struct ioc_cgrp, cpd); |
| } |
| |
| /* |
| * Scale @abs_cost to the inverse of @hw_inuse. The lower the hierarchical |
| * weight, the more expensive each IO. Must round up. |
| */ |
| static u64 abs_cost_to_cost(u64 abs_cost, u32 hw_inuse) |
| { |
| return DIV64_U64_ROUND_UP(abs_cost * WEIGHT_ONE, hw_inuse); |
| } |
| |
| /* |
| * The inverse of abs_cost_to_cost(). Must round up. |
| */ |
| static u64 cost_to_abs_cost(u64 cost, u32 hw_inuse) |
| { |
| return DIV64_U64_ROUND_UP(cost * hw_inuse, WEIGHT_ONE); |
| } |
| |
| static void iocg_commit_bio(struct ioc_gq *iocg, struct bio *bio, |
| u64 abs_cost, u64 cost) |
| { |
| struct iocg_pcpu_stat *gcs; |
| |
| bio->bi_iocost_cost = cost; |
| atomic64_add(cost, &iocg->vtime); |
| |
| gcs = get_cpu_ptr(iocg->pcpu_stat); |
| local64_add(abs_cost, &gcs->abs_vusage); |
| put_cpu_ptr(gcs); |
| } |
| |
| static void iocg_lock(struct ioc_gq *iocg, bool lock_ioc, unsigned long *flags) |
| { |
| if (lock_ioc) { |
| spin_lock_irqsave(&iocg->ioc->lock, *flags); |
| spin_lock(&iocg->waitq.lock); |
| } else { |
| spin_lock_irqsave(&iocg->waitq.lock, *flags); |
| } |
| } |
| |
| static void iocg_unlock(struct ioc_gq *iocg, bool unlock_ioc, unsigned long *flags) |
| { |
| if (unlock_ioc) { |
| spin_unlock(&iocg->waitq.lock); |
| spin_unlock_irqrestore(&iocg->ioc->lock, *flags); |
| } else { |
| spin_unlock_irqrestore(&iocg->waitq.lock, *flags); |
| } |
| } |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/iocost.h> |
| |
| static void ioc_refresh_margins(struct ioc *ioc) |
| { |
| struct ioc_margins *margins = &ioc->margins; |
| u32 period_us = ioc->period_us; |
| u64 vrate = ioc->vtime_base_rate; |
| |
| margins->min = (period_us * MARGIN_MIN_PCT / 100) * vrate; |
| margins->low = (period_us * MARGIN_LOW_PCT / 100) * vrate; |
| margins->target = (period_us * MARGIN_TARGET_PCT / 100) * vrate; |
| } |
| |
| /* latency Qos params changed, update period_us and all the dependent params */ |
| static void ioc_refresh_period_us(struct ioc *ioc) |
| { |
| u32 ppm, lat, multi, period_us; |
| |
| lockdep_assert_held(&ioc->lock); |
| |
| /* pick the higher latency target */ |
| if (ioc->params.qos[QOS_RLAT] >= ioc->params.qos[QOS_WLAT]) { |
| ppm = ioc->params.qos[QOS_RPPM]; |
| lat = ioc->params.qos[QOS_RLAT]; |
| } else { |
| ppm = ioc->params.qos[QOS_WPPM]; |
| lat = ioc->params.qos[QOS_WLAT]; |
| } |
| |
| /* |
| * We want the period to be long enough to contain a healthy number |
| * of IOs while short enough for granular control. Define it as a |
| * multiple of the latency target. Ideally, the multiplier should |
| * be scaled according to the percentile so that it would nominally |
| * contain a certain number of requests. Let's be simpler and |
| * scale it linearly so that it's 2x >= pct(90) and 10x at pct(50). |
| */ |
| if (ppm) |
| multi = max_t(u32, (MILLION - ppm) / 50000, 2); |
| else |
| multi = 2; |
| period_us = multi * lat; |
| period_us = clamp_t(u32, period_us, MIN_PERIOD, MAX_PERIOD); |
| |
| /* calculate dependent params */ |
| ioc->period_us = period_us; |
| ioc->timer_slack_ns = div64_u64( |
| (u64)period_us * NSEC_PER_USEC * TIMER_SLACK_PCT, |
| 100); |
| ioc_refresh_margins(ioc); |
| } |
| |
| /* |
| * ioc->rqos.disk isn't initialized when this function is called from |
| * the init path. |
| */ |
| static int ioc_autop_idx(struct ioc *ioc, struct gendisk *disk) |
| { |
| int idx = ioc->autop_idx; |
| const struct ioc_params *p = &autop[idx]; |
| u32 vrate_pct; |
| u64 now_ns; |
| |
| /* rotational? */ |
| if (!blk_queue_nonrot(disk->queue)) |
| return AUTOP_HDD; |
| |
| /* handle SATA SSDs w/ broken NCQ */ |
| if (blk_queue_depth(disk->queue) == 1) |
| return AUTOP_SSD_QD1; |
| |
| /* use one of the normal ssd sets */ |
| if (idx < AUTOP_SSD_DFL) |
| return AUTOP_SSD_DFL; |
| |
| /* if user is overriding anything, maintain what was there */ |
| if (ioc->user_qos_params || ioc->user_cost_model) |
| return idx; |
| |
| /* step up/down based on the vrate */ |
| vrate_pct = div64_u64(ioc->vtime_base_rate * 100, VTIME_PER_USEC); |
| now_ns = blk_time_get_ns(); |
| |
| if (p->too_fast_vrate_pct && p->too_fast_vrate_pct <= vrate_pct) { |
| if (!ioc->autop_too_fast_at) |
| ioc->autop_too_fast_at = now_ns; |
| if (now_ns - ioc->autop_too_fast_at >= AUTOP_CYCLE_NSEC) |
| return idx + 1; |
| } else { |
| ioc->autop_too_fast_at = 0; |
| } |
| |
| if (p->too_slow_vrate_pct && p->too_slow_vrate_pct >= vrate_pct) { |
| if (!ioc->autop_too_slow_at) |
| ioc->autop_too_slow_at = now_ns; |
| if (now_ns - ioc->autop_too_slow_at >= AUTOP_CYCLE_NSEC) |
| return idx - 1; |
| } else { |
| ioc->autop_too_slow_at = 0; |
| } |
| |
| return idx; |
| } |
| |
| /* |
| * Take the followings as input |
| * |
| * @bps maximum sequential throughput |
| * @seqiops maximum sequential 4k iops |
| * @randiops maximum random 4k iops |
| * |
| * and calculate the linear model cost coefficients. |
| * |
| * *@page per-page cost 1s / (@bps / 4096) |
| * *@seqio base cost of a seq IO max((1s / @seqiops) - *@page, 0) |
| * @randiops base cost of a rand IO max((1s / @randiops) - *@page, 0) |
| */ |
| static void calc_lcoefs(u64 bps, u64 seqiops, u64 randiops, |
| u64 *page, u64 *seqio, u64 *randio) |
| { |
| u64 v; |
| |
| *page = *seqio = *randio = 0; |
| |
| if (bps) { |
| u64 bps_pages = DIV_ROUND_UP_ULL(bps, IOC_PAGE_SIZE); |
| |
| if (bps_pages) |
| *page = DIV64_U64_ROUND_UP(VTIME_PER_SEC, bps_pages); |
| else |
| *page = 1; |
| } |
| |
| if (seqiops) { |
| v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, seqiops); |
| if (v > *page) |
| *seqio = v - *page; |
| } |
| |
| if (randiops) { |
| v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, randiops); |
| if (v > *page) |
| *randio = v - *page; |
| } |
| } |
| |
| static void ioc_refresh_lcoefs(struct ioc *ioc) |
| { |
| u64 *u = ioc->params.i_lcoefs; |
| u64 *c = ioc->params.lcoefs; |
| |
| calc_lcoefs(u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS], |
| &c[LCOEF_RPAGE], &c[LCOEF_RSEQIO], &c[LCOEF_RRANDIO]); |
| calc_lcoefs(u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS], |
| &c[LCOEF_WPAGE], &c[LCOEF_WSEQIO], &c[LCOEF_WRANDIO]); |
| } |
| |
| /* |
| * struct gendisk is required as an argument because ioc->rqos.disk |
| * is not properly initialized when called from the init path. |
| */ |
| static bool ioc_refresh_params_disk(struct ioc *ioc, bool force, |
| struct gendisk *disk) |
| { |
| const struct ioc_params *p; |
| int idx; |
| |
| lockdep_assert_held(&ioc->lock); |
| |
| idx = ioc_autop_idx(ioc, disk); |
| p = &autop[idx]; |
| |
| if (idx == ioc->autop_idx && !force) |
| return false; |
| |
| if (idx != ioc->autop_idx) { |
| atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC); |
| ioc->vtime_base_rate = VTIME_PER_USEC; |
| } |
| |
| ioc->autop_idx = idx; |
| ioc->autop_too_fast_at = 0; |
| ioc->autop_too_slow_at = 0; |
| |
| if (!ioc->user_qos_params) |
| memcpy(ioc->params.qos, p->qos, sizeof(p->qos)); |
| if (!ioc->user_cost_model) |
| memcpy(ioc->params.i_lcoefs, p->i_lcoefs, sizeof(p->i_lcoefs)); |
| |
| ioc_refresh_period_us(ioc); |
| ioc_refresh_lcoefs(ioc); |
| |
| ioc->vrate_min = DIV64_U64_ROUND_UP((u64)ioc->params.qos[QOS_MIN] * |
| VTIME_PER_USEC, MILLION); |
| ioc->vrate_max = DIV64_U64_ROUND_UP((u64)ioc->params.qos[QOS_MAX] * |
| VTIME_PER_USEC, MILLION); |
| |
| return true; |
| } |
| |
| static bool ioc_refresh_params(struct ioc *ioc, bool force) |
| { |
| return ioc_refresh_params_disk(ioc, force, ioc->rqos.disk); |
| } |
| |
| /* |
| * When an iocg accumulates too much vtime or gets deactivated, we throw away |
| * some vtime, which lowers the overall device utilization. As the exact amount |
| * which is being thrown away is known, we can compensate by accelerating the |
| * vrate accordingly so that the extra vtime generated in the current period |
| * matches what got lost. |
| */ |
| static void ioc_refresh_vrate(struct ioc *ioc, struct ioc_now *now) |
| { |
| s64 pleft = ioc->period_at + ioc->period_us - now->now; |
| s64 vperiod = ioc->period_us * ioc->vtime_base_rate; |
| s64 vcomp, vcomp_min, vcomp_max; |
| |
| lockdep_assert_held(&ioc->lock); |
| |
| /* we need some time left in this period */ |
| if (pleft <= 0) |
| goto done; |
| |
| /* |
| * Calculate how much vrate should be adjusted to offset the error. |
| * Limit the amount of adjustment and deduct the adjusted amount from |
| * the error. |
| */ |
| vcomp = -div64_s64(ioc->vtime_err, pleft); |
| vcomp_min = -(ioc->vtime_base_rate >> 1); |
| vcomp_max = ioc->vtime_base_rate; |
| vcomp = clamp(vcomp, vcomp_min, vcomp_max); |
| |
| ioc->vtime_err += vcomp * pleft; |
| |
| atomic64_set(&ioc->vtime_rate, ioc->vtime_base_rate + vcomp); |
| done: |
| /* bound how much error can accumulate */ |
| ioc->vtime_err = clamp(ioc->vtime_err, -vperiod, vperiod); |
| } |
| |
| static void ioc_adjust_base_vrate(struct ioc *ioc, u32 rq_wait_pct, |
| int nr_lagging, int nr_shortages, |
| int prev_busy_level, u32 *missed_ppm) |
| { |
| u64 vrate = ioc->vtime_base_rate; |
| u64 vrate_min = ioc->vrate_min, vrate_max = ioc->vrate_max; |
| |
| if (!ioc->busy_level || (ioc->busy_level < 0 && nr_lagging)) { |
| if (ioc->busy_level != prev_busy_level || nr_lagging) |
| trace_iocost_ioc_vrate_adj(ioc, vrate, |
| missed_ppm, rq_wait_pct, |
| nr_lagging, nr_shortages); |
| |
| return; |
| } |
| |
| /* |
| * If vrate is out of bounds, apply clamp gradually as the |
| * bounds can change abruptly. Otherwise, apply busy_level |
| * based adjustment. |
| */ |
| if (vrate < vrate_min) { |
| vrate = div64_u64(vrate * (100 + VRATE_CLAMP_ADJ_PCT), 100); |
| vrate = min(vrate, vrate_min); |
| } else if (vrate > vrate_max) { |
| vrate = div64_u64(vrate * (100 - VRATE_CLAMP_ADJ_PCT), 100); |
| vrate = max(vrate, vrate_max); |
| } else { |
| int idx = min_t(int, abs(ioc->busy_level), |
| ARRAY_SIZE(vrate_adj_pct) - 1); |
| u32 adj_pct = vrate_adj_pct[idx]; |
| |
| if (ioc->busy_level > 0) |
| adj_pct = 100 - adj_pct; |
| else |
| adj_pct = 100 + adj_pct; |
| |
| vrate = clamp(DIV64_U64_ROUND_UP(vrate * adj_pct, 100), |
| vrate_min, vrate_max); |
| } |
| |
| trace_iocost_ioc_vrate_adj(ioc, vrate, missed_ppm, rq_wait_pct, |
| nr_lagging, nr_shortages); |
| |
| ioc->vtime_base_rate = vrate; |
| ioc_refresh_margins(ioc); |
| } |
| |
| /* take a snapshot of the current [v]time and vrate */ |
| static void ioc_now(struct ioc *ioc, struct ioc_now *now) |
| { |
| unsigned seq; |
| u64 vrate; |
| |
| now->now_ns = blk_time_get_ns(); |
| now->now = ktime_to_us(now->now_ns); |
| vrate = atomic64_read(&ioc->vtime_rate); |
| |
| /* |
| * The current vtime is |
| * |
| * vtime at period start + (wallclock time since the start) * vrate |
| * |
| * As a consistent snapshot of `period_at_vtime` and `period_at` is |
| * needed, they're seqcount protected. |
| */ |
| do { |
| seq = read_seqcount_begin(&ioc->period_seqcount); |
| now->vnow = ioc->period_at_vtime + |
| (now->now - ioc->period_at) * vrate; |
| } while (read_seqcount_retry(&ioc->period_seqcount, seq)); |
| } |
| |
| static void ioc_start_period(struct ioc *ioc, struct ioc_now *now) |
| { |
| WARN_ON_ONCE(ioc->running != IOC_RUNNING); |
| |
| write_seqcount_begin(&ioc->period_seqcount); |
| ioc->period_at = now->now; |
| ioc->period_at_vtime = now->vnow; |
| write_seqcount_end(&ioc->period_seqcount); |
| |
| ioc->timer.expires = jiffies + usecs_to_jiffies(ioc->period_us); |
| add_timer(&ioc->timer); |
| } |
| |
| /* |
| * Update @iocg's `active` and `inuse` to @active and @inuse, update level |
| * weight sums and propagate upwards accordingly. If @save, the current margin |
| * is saved to be used as reference for later inuse in-period adjustments. |
| */ |
| static void __propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse, |
| bool save, struct ioc_now *now) |
| { |
| struct ioc *ioc = iocg->ioc; |
| int lvl; |
| |
| lockdep_assert_held(&ioc->lock); |
| |
| /* |
| * For an active leaf node, its inuse shouldn't be zero or exceed |
| * @active. An active internal node's inuse is solely determined by the |
| * inuse to active ratio of its children regardless of @inuse. |
| */ |
| if (list_empty(&iocg->active_list) && iocg->child_active_sum) { |
| inuse = DIV64_U64_ROUND_UP(active * iocg->child_inuse_sum, |
| iocg->child_active_sum); |
| } else { |
| inuse = clamp_t(u32, inuse, 1, active); |
| } |
| |
| iocg->last_inuse = iocg->inuse; |
| if (save) |
| iocg->saved_margin = now->vnow - atomic64_read(&iocg->vtime); |
| |
| if (active == iocg->active && inuse == iocg->inuse) |
| return; |
| |
| for (lvl = iocg->level - 1; lvl >= 0; lvl--) { |
| struct ioc_gq *parent = iocg->ancestors[lvl]; |
| struct ioc_gq *child = iocg->ancestors[lvl + 1]; |
| u32 parent_active = 0, parent_inuse = 0; |
| |
| /* update the level sums */ |
| parent->child_active_sum += (s32)(active - child->active); |
| parent->child_inuse_sum += (s32)(inuse - child->inuse); |
| /* apply the updates */ |
| child->active = active; |
| child->inuse = inuse; |
| |
| /* |
| * The delta between inuse and active sums indicates that |
| * much of weight is being given away. Parent's inuse |
| * and active should reflect the ratio. |
| */ |
| if (parent->child_active_sum) { |
| parent_active = parent->weight; |
| parent_inuse = DIV64_U64_ROUND_UP( |
| parent_active * parent->child_inuse_sum, |
| parent->child_active_sum); |
| } |
| |
| /* do we need to keep walking up? */ |
| if (parent_active == parent->active && |
| parent_inuse == parent->inuse) |
| break; |
| |
| active = parent_active; |
| inuse = parent_inuse; |
| } |
| |
| ioc->weights_updated = true; |
| } |
| |
| static void commit_weights(struct ioc *ioc) |
| { |
| lockdep_assert_held(&ioc->lock); |
| |
| if (ioc->weights_updated) { |
| /* paired with rmb in current_hweight(), see there */ |
| smp_wmb(); |
| atomic_inc(&ioc->hweight_gen); |
| ioc->weights_updated = false; |
| } |
| } |
| |
| static void propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse, |
| bool save, struct ioc_now *now) |
| { |
| __propagate_weights(iocg, active, inuse, save, now); |
| commit_weights(iocg->ioc); |
| } |
| |
| static void current_hweight(struct ioc_gq *iocg, u32 *hw_activep, u32 *hw_inusep) |
| { |
| struct ioc *ioc = iocg->ioc; |
| int lvl; |
| u32 hwa, hwi; |
| int ioc_gen; |
| |
| /* hot path - if uptodate, use cached */ |
| ioc_gen = atomic_read(&ioc->hweight_gen); |
| if (ioc_gen == iocg->hweight_gen) |
| goto out; |
| |
| /* |
| * Paired with wmb in commit_weights(). If we saw the updated |
| * hweight_gen, all the weight updates from __propagate_weights() are |
| * visible too. |
| * |
| * We can race with weight updates during calculation and get it |
| * wrong. However, hweight_gen would have changed and a future |
| * reader will recalculate and we're guaranteed to discard the |
| * wrong result soon. |
| */ |
| smp_rmb(); |
| |
| hwa = hwi = WEIGHT_ONE; |
| for (lvl = 0; lvl <= iocg->level - 1; lvl++) { |
| struct ioc_gq *parent = iocg->ancestors[lvl]; |
| struct ioc_gq *child = iocg->ancestors[lvl + 1]; |
| u64 active_sum = READ_ONCE(parent->child_active_sum); |
| u64 inuse_sum = READ_ONCE(parent->child_inuse_sum); |
| u32 active = READ_ONCE(child->active); |
| u32 inuse = READ_ONCE(child->inuse); |
| |
| /* we can race with deactivations and either may read as zero */ |
| if (!active_sum || !inuse_sum) |
| continue; |
| |
| active_sum = max_t(u64, active, active_sum); |
| hwa = div64_u64((u64)hwa * active, active_sum); |
| |
| inuse_sum = max_t(u64, inuse, inuse_sum); |
| hwi = div64_u64((u64)hwi * inuse, inuse_sum); |
| } |
| |
| iocg->hweight_active = max_t(u32, hwa, 1); |
| iocg->hweight_inuse = max_t(u32, hwi, 1); |
| iocg->hweight_gen = ioc_gen; |
| out: |
| if (hw_activep) |
| *hw_activep = iocg->hweight_active; |
| if (hw_inusep) |
| *hw_inusep = iocg->hweight_inuse; |
| } |
| |
| /* |
| * Calculate the hweight_inuse @iocg would get with max @inuse assuming all the |
| * other weights stay unchanged. |
| */ |
| static u32 current_hweight_max(struct ioc_gq *iocg) |
| { |
| u32 hwm = WEIGHT_ONE; |
| u32 inuse = iocg->active; |
| u64 child_inuse_sum; |
| int lvl; |
| |
| lockdep_assert_held(&iocg->ioc->lock); |
| |
| for (lvl = iocg->level - 1; lvl >= 0; lvl--) { |
| struct ioc_gq *parent = iocg->ancestors[lvl]; |
| struct ioc_gq *child = iocg->ancestors[lvl + 1]; |
| |
| child_inuse_sum = parent->child_inuse_sum + inuse - child->inuse; |
| hwm = div64_u64((u64)hwm * inuse, child_inuse_sum); |
| inuse = DIV64_U64_ROUND_UP(parent->active * child_inuse_sum, |
| parent->child_active_sum); |
| } |
| |
| return max_t(u32, hwm, 1); |
| } |
| |
| static void weight_updated(struct ioc_gq *iocg, struct ioc_now *now) |
| { |
| struct ioc *ioc = iocg->ioc; |
| struct blkcg_gq *blkg = iocg_to_blkg(iocg); |
| struct ioc_cgrp *iocc = blkcg_to_iocc(blkg->blkcg); |
| u32 weight; |
| |
| lockdep_assert_held(&ioc->lock); |
| |
| weight = iocg->cfg_weight ?: iocc->dfl_weight; |
| if (weight != iocg->weight && iocg->active) |
| propagate_weights(iocg, weight, iocg->inuse, true, now); |
| iocg->weight = weight; |
| } |
| |
| static bool iocg_activate(struct ioc_gq *iocg, struct ioc_now *now) |
| { |
| struct ioc *ioc = iocg->ioc; |
| u64 __maybe_unused last_period, cur_period; |
| u64 vtime, vtarget; |
| int i; |
| |
| /* |
| * If seem to be already active, just update the stamp to tell the |
| * timer that we're still active. We don't mind occassional races. |
| */ |
| if (!list_empty(&iocg->active_list)) { |
| ioc_now(ioc, now); |
| cur_period = atomic64_read(&ioc->cur_period); |
| if (atomic64_read(&iocg->active_period) != cur_period) |
| atomic64_set(&iocg->active_period, cur_period); |
| return true; |
| } |
| |
| /* racy check on internal node IOs, treat as root level IOs */ |
| if (iocg->child_active_sum) |
| return false; |
| |
| spin_lock_irq(&ioc->lock); |
| |
| ioc_now(ioc, now); |
| |
| /* update period */ |
| cur_period = atomic64_read(&ioc->cur_period); |
| last_period = atomic64_read(&iocg->active_period); |
| atomic64_set(&iocg->active_period, cur_period); |
| |
| /* already activated or breaking leaf-only constraint? */ |
| if (!list_empty(&iocg->active_list)) |
| goto succeed_unlock; |
| for (i = iocg->level - 1; i > 0; i--) |
| if (!list_empty(&iocg->ancestors[i]->active_list)) |
| goto fail_unlock; |
| |
| if (iocg->child_active_sum) |
| goto fail_unlock; |
| |
| /* |
| * Always start with the target budget. On deactivation, we throw away |
| * anything above it. |
| */ |
| vtarget = now->vnow - ioc->margins.target; |
| vtime = atomic64_read(&iocg->vtime); |
| |
| atomic64_add(vtarget - vtime, &iocg->vtime); |
| atomic64_add(vtarget - vtime, &iocg->done_vtime); |
| vtime = vtarget; |
| |
| /* |
| * Activate, propagate weight and start period timer if not |
| * running. Reset hweight_gen to avoid accidental match from |
| * wrapping. |
| */ |
| iocg->hweight_gen = atomic_read(&ioc->hweight_gen) - 1; |
| list_add(&iocg->active_list, &ioc->active_iocgs); |
| |
| propagate_weights(iocg, iocg->weight, |
| iocg->last_inuse ?: iocg->weight, true, now); |
| |
| TRACE_IOCG_PATH(iocg_activate, iocg, now, |
| last_period, cur_period, vtime); |
| |
| iocg->activated_at = now->now; |
| |
| if (ioc->running == IOC_IDLE) { |
| ioc->running = IOC_RUNNING; |
| ioc->dfgv_period_at = now->now; |
| ioc->dfgv_period_rem = 0; |
| ioc_start_period(ioc, now); |
| } |
| |
| succeed_unlock: |
| spin_unlock_irq(&ioc->lock); |
| return true; |
| |
| fail_unlock: |
| spin_unlock_irq(&ioc->lock); |
| return false; |
| } |
| |
| static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now) |
| { |
| struct ioc *ioc = iocg->ioc; |
| struct blkcg_gq *blkg = iocg_to_blkg(iocg); |
| u64 tdelta, delay, new_delay, shift; |
| s64 vover, vover_pct; |
| u32 hwa; |
| |
| lockdep_assert_held(&iocg->waitq.lock); |
| |
| /* |
| * If the delay is set by another CPU, we may be in the past. No need to |
| * change anything if so. This avoids decay calculation underflow. |
| */ |
| if (time_before64(now->now, iocg->delay_at)) |
| return false; |
| |
| /* calculate the current delay in effect - 1/2 every second */ |
| tdelta = now->now - iocg->delay_at; |
| shift = div64_u64(tdelta, USEC_PER_SEC); |
| if (iocg->delay && shift < BITS_PER_LONG) |
| delay = iocg->delay >> shift; |
| else |
| delay = 0; |
| |
| /* calculate the new delay from the debt amount */ |
| current_hweight(iocg, &hwa, NULL); |
| vover = atomic64_read(&iocg->vtime) + |
| abs_cost_to_cost(iocg->abs_vdebt, hwa) - now->vnow; |
| vover_pct = div64_s64(100 * vover, |
| ioc->period_us * ioc->vtime_base_rate); |
| |
| if (vover_pct <= MIN_DELAY_THR_PCT) |
| new_delay = 0; |
| else if (vover_pct >= MAX_DELAY_THR_PCT) |
| new_delay = MAX_DELAY; |
| else |
| new_delay = MIN_DELAY + |
| div_u64((MAX_DELAY - MIN_DELAY) * |
| (vover_pct - MIN_DELAY_THR_PCT), |
| MAX_DELAY_THR_PCT - MIN_DELAY_THR_PCT); |
| |
| /* pick the higher one and apply */ |
| if (new_delay > delay) { |
| iocg->delay = new_delay; |
| iocg->delay_at = now->now; |
| delay = new_delay; |
| } |
| |
| if (delay >= MIN_DELAY) { |
| if (!iocg->indelay_since) |
| iocg->indelay_since = now->now; |
| blkcg_set_delay(blkg, delay * NSEC_PER_USEC); |
| return true; |
| } else { |
| if (iocg->indelay_since) { |
| iocg->stat.indelay_us += now->now - iocg->indelay_since; |
| iocg->indelay_since = 0; |
| } |
| iocg->delay = 0; |
| blkcg_clear_delay(blkg); |
| return false; |
| } |
| } |
| |
| static void iocg_incur_debt(struct ioc_gq *iocg, u64 abs_cost, |
| struct ioc_now *now) |
| { |
| struct iocg_pcpu_stat *gcs; |
| |
| lockdep_assert_held(&iocg->ioc->lock); |
| lockdep_assert_held(&iocg->waitq.lock); |
| WARN_ON_ONCE(list_empty(&iocg->active_list)); |
| |
| /* |
| * Once in debt, debt handling owns inuse. @iocg stays at the minimum |
| * inuse donating all of it share to others until its debt is paid off. |
| */ |
| if (!iocg->abs_vdebt && abs_cost) { |
| iocg->indebt_since = now->now; |
| propagate_weights(iocg, iocg->active, 0, false, now); |
| } |
| |
| iocg->abs_vdebt += abs_cost; |
| |
| gcs = get_cpu_ptr(iocg->pcpu_stat); |
| local64_add(abs_cost, &gcs->abs_vusage); |
| put_cpu_ptr(gcs); |
| } |
| |
| static void iocg_pay_debt(struct ioc_gq *iocg, u64 abs_vpay, |
| struct ioc_now *now) |
| { |
| lockdep_assert_held(&iocg->ioc->lock); |
| lockdep_assert_held(&iocg->waitq.lock); |
| |
| /* |
| * make sure that nobody messed with @iocg. Check iocg->pd.online |
| * to avoid warn when removing blkcg or disk. |
| */ |
| WARN_ON_ONCE(list_empty(&iocg->active_list) && iocg->pd.online); |
| WARN_ON_ONCE(iocg->inuse > 1); |
| |
| iocg->abs_vdebt -= min(abs_vpay, iocg->abs_vdebt); |
| |
| /* if debt is paid in full, restore inuse */ |
| if (!iocg->abs_vdebt) { |
| iocg->stat.indebt_us += now->now - iocg->indebt_since; |
| iocg->indebt_since = 0; |
| |
| propagate_weights(iocg, iocg->active, iocg->last_inuse, |
| false, now); |
| } |
| } |
| |
| static int iocg_wake_fn(struct wait_queue_entry *wq_entry, unsigned mode, |
| int flags, void *key) |
| { |
| struct iocg_wait *wait = container_of(wq_entry, struct iocg_wait, wait); |
| struct iocg_wake_ctx *ctx = key; |
| u64 cost = abs_cost_to_cost(wait->abs_cost, ctx->hw_inuse); |
| |
| ctx->vbudget -= cost; |
| |
| if (ctx->vbudget < 0) |
| return -1; |
| |
| iocg_commit_bio(ctx->iocg, wait->bio, wait->abs_cost, cost); |
| wait->committed = true; |
| |
| /* |
| * autoremove_wake_function() removes the wait entry only when it |
| * actually changed the task state. We want the wait always removed. |
| * Remove explicitly and use default_wake_function(). Note that the |
| * order of operations is important as finish_wait() tests whether |
| * @wq_entry is removed without grabbing the lock. |
| */ |
| default_wake_function(wq_entry, mode, flags, key); |
| list_del_init_careful(&wq_entry->entry); |
| return 0; |
| } |
| |
| /* |
| * Calculate the accumulated budget, pay debt if @pay_debt and wake up waiters |
| * accordingly. When @pay_debt is %true, the caller must be holding ioc->lock in |
| * addition to iocg->waitq.lock. |
| */ |
| static void iocg_kick_waitq(struct ioc_gq *iocg, bool pay_debt, |
| struct ioc_now *now) |
| { |
| struct ioc *ioc = iocg->ioc; |
| struct iocg_wake_ctx ctx = { .iocg = iocg }; |
| u64 vshortage, expires, oexpires; |
| s64 vbudget; |
| u32 hwa; |
| |
| lockdep_assert_held(&iocg->waitq.lock); |
| |
| current_hweight(iocg, &hwa, NULL); |
| vbudget = now->vnow - atomic64_read(&iocg->vtime); |
| |
| /* pay off debt */ |
| if (pay_debt && iocg->abs_vdebt && vbudget > 0) { |
| u64 abs_vbudget = cost_to_abs_cost(vbudget, hwa); |
| u64 abs_vpay = min_t(u64, abs_vbudget, iocg->abs_vdebt); |
| u64 vpay = abs_cost_to_cost(abs_vpay, hwa); |
| |
| lockdep_assert_held(&ioc->lock); |
| |
| atomic64_add(vpay, &iocg->vtime); |
| atomic64_add(vpay, &iocg->done_vtime); |
| iocg_pay_debt(iocg, abs_vpay, now); |
| vbudget -= vpay; |
| } |
| |
| if (iocg->abs_vdebt || iocg->delay) |
| iocg_kick_delay(iocg, now); |
| |
| /* |
| * Debt can still be outstanding if we haven't paid all yet or the |
| * caller raced and called without @pay_debt. Shouldn't wake up waiters |
| * under debt. Make sure @vbudget reflects the outstanding amount and is |
| * not positive. |
| */ |
| if (iocg->abs_vdebt) { |
| s64 vdebt = abs_cost_to_cost(iocg->abs_vdebt, hwa); |
| vbudget = min_t(s64, 0, vbudget - vdebt); |
| } |
| |
| /* |
| * Wake up the ones which are due and see how much vtime we'll need for |
| * the next one. As paying off debt restores hw_inuse, it must be read |
| * after the above debt payment. |
| */ |
| ctx.vbudget = vbudget; |
| current_hweight(iocg, NULL, &ctx.hw_inuse); |
| |
| __wake_up_locked_key(&iocg->waitq, TASK_NORMAL, &ctx); |
| |
| if (!waitqueue_active(&iocg->waitq)) { |
| if (iocg->wait_since) { |
| iocg->stat.wait_us += now->now - iocg->wait_since; |
| iocg->wait_since = 0; |
| } |
| return; |
| } |
| |
| if (!iocg->wait_since) |
| iocg->wait_since = now->now; |
| |
| if (WARN_ON_ONCE(ctx.vbudget >= 0)) |
| return; |
| |
| /* determine next wakeup, add a timer margin to guarantee chunking */ |
| vshortage = -ctx.vbudget; |
| expires = now->now_ns + |
| DIV64_U64_ROUND_UP(vshortage, ioc->vtime_base_rate) * |
| NSEC_PER_USEC; |
| expires += ioc->timer_slack_ns; |
| |
| /* if already active and close enough, don't bother */ |
| oexpires = ktime_to_ns(hrtimer_get_softexpires(&iocg->waitq_timer)); |
| if (hrtimer_is_queued(&iocg->waitq_timer) && |
| abs(oexpires - expires) <= ioc->timer_slack_ns) |
| return; |
| |
| hrtimer_start_range_ns(&iocg->waitq_timer, ns_to_ktime(expires), |
| ioc->timer_slack_ns, HRTIMER_MODE_ABS); |
| } |
| |
| static enum hrtimer_restart iocg_waitq_timer_fn(struct hrtimer *timer) |
| { |
| struct ioc_gq *iocg = container_of(timer, struct ioc_gq, waitq_timer); |
| bool pay_debt = READ_ONCE(iocg->abs_vdebt); |
| struct ioc_now now; |
| unsigned long flags; |
| |
| ioc_now(iocg->ioc, &now); |
| |
| iocg_lock(iocg, pay_debt, &flags); |
| iocg_kick_waitq(iocg, pay_debt, &now); |
| iocg_unlock(iocg, pay_debt, &flags); |
| |
| return HRTIMER_NORESTART; |
| } |
| |
| static void ioc_lat_stat(struct ioc *ioc, u32 *missed_ppm_ar, u32 *rq_wait_pct_p) |
| { |
| u32 nr_met[2] = { }; |
| u32 nr_missed[2] = { }; |
| u64 rq_wait_ns = 0; |
| int cpu, rw; |
| |
| for_each_online_cpu(cpu) { |
| struct ioc_pcpu_stat *stat = per_cpu_ptr(ioc->pcpu_stat, cpu); |
| u64 this_rq_wait_ns; |
| |
| for (rw = READ; rw <= WRITE; rw++) { |
| u32 this_met = local_read(&stat->missed[rw].nr_met); |
| u32 this_missed = local_read(&stat->missed[rw].nr_missed); |
| |
| nr_met[rw] += this_met - stat->missed[rw].last_met; |
| nr_missed[rw] += this_missed - stat->missed[rw].last_missed; |
| stat->missed[rw].last_met = this_met; |
| stat->missed[rw].last_missed = this_missed; |
| } |
| |
| this_rq_wait_ns = local64_read(&stat->rq_wait_ns); |
| rq_wait_ns += this_rq_wait_ns - stat->last_rq_wait_ns; |
| stat->last_rq_wait_ns = this_rq_wait_ns; |
| } |
| |
| for (rw = READ; rw <= WRITE; rw++) { |
| if (nr_met[rw] + nr_missed[rw]) |
| missed_ppm_ar[rw] = |
| DIV64_U64_ROUND_UP((u64)nr_missed[rw] * MILLION, |
| nr_met[rw] + nr_missed[rw]); |
| else |
| missed_ppm_ar[rw] = 0; |
| } |
| |
| *rq_wait_pct_p = div64_u64(rq_wait_ns * 100, |
| ioc->period_us * NSEC_PER_USEC); |
| } |
| |
| /* was iocg idle this period? */ |
| static bool iocg_is_idle(struct ioc_gq *iocg) |
| { |
| struct ioc *ioc = iocg->ioc; |
| |
| /* did something get issued this period? */ |
| if (atomic64_read(&iocg->active_period) == |
| atomic64_read(&ioc->cur_period)) |
| return false; |
| |
| /* is something in flight? */ |
| if (atomic64_read(&iocg->done_vtime) != atomic64_read(&iocg->vtime)) |
| return false; |
| |
| return true; |
| } |
| |
| /* |
| * Call this function on the target leaf @iocg's to build pre-order traversal |
| * list of all the ancestors in @inner_walk. The inner nodes are linked through |
| * ->walk_list and the caller is responsible for dissolving the list after use. |
| */ |
| static void iocg_build_inner_walk(struct ioc_gq *iocg, |
| struct list_head *inner_walk) |
| { |
| int lvl; |
| |
| WARN_ON_ONCE(!list_empty(&iocg->walk_list)); |
| |
| /* find the first ancestor which hasn't been visited yet */ |
| for (lvl = iocg->level - 1; lvl >= 0; lvl--) { |
| if (!list_empty(&iocg->ancestors[lvl]->walk_list)) |
| break; |
| } |
| |
| /* walk down and visit the inner nodes to get pre-order traversal */ |
| while (++lvl <= iocg->level - 1) { |
| struct ioc_gq *inner = iocg->ancestors[lvl]; |
| |
| /* record traversal order */ |
| list_add_tail(&inner->walk_list, inner_walk); |
| } |
| } |
| |
| /* propagate the deltas to the parent */ |
| static void iocg_flush_stat_upward(struct ioc_gq *iocg) |
| { |
| if (iocg->level > 0) { |
| struct iocg_stat *parent_stat = |
| &iocg->ancestors[iocg->level - 1]->stat; |
| |
| parent_stat->usage_us += |
| iocg->stat.usage_us - iocg->last_stat.usage_us; |
| parent_stat->wait_us += |
| iocg->stat.wait_us - iocg->last_stat.wait_us; |
| parent_stat->indebt_us += |
| iocg->stat.indebt_us - iocg->last_stat.indebt_us; |
| parent_stat->indelay_us += |
| iocg->stat.indelay_us - iocg->last_stat.indelay_us; |
| } |
| |
| iocg->last_stat = iocg->stat; |
| } |
| |
| /* collect per-cpu counters and propagate the deltas to the parent */ |
| static void iocg_flush_stat_leaf(struct ioc_gq *iocg, struct ioc_now *now) |
| { |
| struct ioc *ioc = iocg->ioc; |
| u64 abs_vusage = 0; |
| u64 vusage_delta; |
| int cpu; |
| |
| lockdep_assert_held(&iocg->ioc->lock); |
| |
| /* collect per-cpu counters */ |
| for_each_possible_cpu(cpu) { |
| abs_vusage += local64_read( |
| per_cpu_ptr(&iocg->pcpu_stat->abs_vusage, cpu)); |
| } |
| vusage_delta = abs_vusage - iocg->last_stat_abs_vusage; |
| iocg->last_stat_abs_vusage = abs_vusage; |
| |
| iocg->usage_delta_us = div64_u64(vusage_delta, ioc->vtime_base_rate); |
| iocg->stat.usage_us += iocg->usage_delta_us; |
| |
| iocg_flush_stat_upward(iocg); |
| } |
| |
| /* get stat counters ready for reading on all active iocgs */ |
| static void iocg_flush_stat(struct list_head *target_iocgs, struct ioc_now *now) |
| { |
| LIST_HEAD(inner_walk); |
| struct ioc_gq *iocg, *tiocg; |
| |
| /* flush leaves and build inner node walk list */ |
| list_for_each_entry(iocg, target_iocgs, active_list) { |
| iocg_flush_stat_leaf(iocg, now); |
| iocg_build_inner_walk(iocg, &inner_walk); |
| } |
| |
| /* keep flushing upwards by walking the inner list backwards */ |
| list_for_each_entry_safe_reverse(iocg, tiocg, &inner_walk, walk_list) { |
| iocg_flush_stat_upward(iocg); |
| list_del_init(&iocg->walk_list); |
| } |
| } |
| |
| /* |
| * Determine what @iocg's hweight_inuse should be after donating unused |
| * capacity. @hwm is the upper bound and used to signal no donation. This |
| * function also throws away @iocg's excess budget. |
| */ |
| static u32 hweight_after_donation(struct ioc_gq *iocg, u32 old_hwi, u32 hwm, |
| u32 usage, struct ioc_now *now) |
| { |
| struct ioc *ioc = iocg->ioc; |
| u64 vtime = atomic64_read(&iocg->vtime); |
| s64 excess, delta, target, new_hwi; |
| |
| /* debt handling owns inuse for debtors */ |
| if (iocg->abs_vdebt) |
| return 1; |
| |
| /* see whether minimum margin requirement is met */ |
| if (waitqueue_active(&iocg->waitq) || |
| time_after64(vtime, now->vnow - ioc->margins.min)) |
| return hwm; |
| |
| /* throw away excess above target */ |
| excess = now->vnow - vtime - ioc->margins.target; |
| if (excess > 0) { |
| atomic64_add(excess, &iocg->vtime); |
| atomic64_add(excess, &iocg->done_vtime); |
| vtime += excess; |
| ioc->vtime_err -= div64_u64(excess * old_hwi, WEIGHT_ONE); |
| } |
| |
| /* |
| * Let's say the distance between iocg's and device's vtimes as a |
| * fraction of period duration is delta. Assuming that the iocg will |
| * consume the usage determined above, we want to determine new_hwi so |
| * that delta equals MARGIN_TARGET at the end of the next period. |
| * |
| * We need to execute usage worth of IOs while spending the sum of the |
| * new budget (1 - MARGIN_TARGET) and the leftover from the last period |
| * (delta): |
| * |
| * usage = (1 - MARGIN_TARGET + delta) * new_hwi |
| * |
| * Therefore, the new_hwi is: |
| * |
| * new_hwi = usage / (1 - MARGIN_TARGET + delta) |
| */ |
| delta = div64_s64(WEIGHT_ONE * (now->vnow - vtime), |
| now->vnow - ioc->period_at_vtime); |
| target = WEIGHT_ONE * MARGIN_TARGET_PCT / 100; |
| new_hwi = div64_s64(WEIGHT_ONE * usage, WEIGHT_ONE - target + delta); |
| |
| return clamp_t(s64, new_hwi, 1, hwm); |
| } |
| |
| /* |
| * For work-conservation, an iocg which isn't using all of its share should |
| * donate the leftover to other iocgs. There are two ways to achieve this - 1. |
| * bumping up vrate accordingly 2. lowering the donating iocg's inuse weight. |
| * |
| * #1 is mathematically simpler but has the drawback of requiring synchronous |
| * global hweight_inuse updates when idle iocg's get activated or inuse weights |
| * change due to donation snapbacks as it has the possibility of grossly |
| * overshooting what's allowed by the model and vrate. |
| * |
| * #2 is inherently safe with local operations. The donating iocg can easily |
| * snap back to higher weights when needed without worrying about impacts on |
| * other nodes as the impacts will be inherently correct. This also makes idle |
| * iocg activations safe. The only effect activations have is decreasing |
| * hweight_inuse of others, the right solution to which is for those iocgs to |
| * snap back to higher weights. |
| * |
| * So, we go with #2. The challenge is calculating how each donating iocg's |
| * inuse should be adjusted to achieve the target donation amounts. This is done |
| * using Andy's method described in the following pdf. |
| * |
| * https://drive.google.com/file/d/1PsJwxPFtjUnwOY1QJ5AeICCcsL7BM3bo |
| * |
| * Given the weights and target after-donation hweight_inuse values, Andy's |
| * method determines how the proportional distribution should look like at each |
| * sibling level to maintain the relative relationship between all non-donating |
| * pairs. To roughly summarize, it divides the tree into donating and |
| * non-donating parts, calculates global donation rate which is used to |
| * determine the target hweight_inuse for each node, and then derives per-level |
| * proportions. |
| * |
| * The following pdf shows that global distribution calculated this way can be |
| * achieved by scaling inuse weights of donating leaves and propagating the |
| * adjustments upwards proportionally. |
| * |
| * https://drive.google.com/file/d/1vONz1-fzVO7oY5DXXsLjSxEtYYQbOvsE |
| * |
| * Combining the above two, we can determine how each leaf iocg's inuse should |
| * be adjusted to achieve the target donation. |
| * |
| * https://drive.google.com/file/d/1WcrltBOSPN0qXVdBgnKm4mdp9FhuEFQN |
| * |
| * The inline comments use symbols from the last pdf. |
| * |
| * b is the sum of the absolute budgets in the subtree. 1 for the root node. |
| * f is the sum of the absolute budgets of non-donating nodes in the subtree. |
| * t is the sum of the absolute budgets of donating nodes in the subtree. |
| * w is the weight of the node. w = w_f + w_t |
| * w_f is the non-donating portion of w. w_f = w * f / b |
| * w_b is the donating portion of w. w_t = w * t / b |
| * s is the sum of all sibling weights. s = Sum(w) for siblings |
| * s_f and s_t are the non-donating and donating portions of s. |
| * |
| * Subscript p denotes the parent's counterpart and ' the adjusted value - e.g. |
| * w_pt is the donating portion of the parent's weight and w'_pt the same value |
| * after adjustments. Subscript r denotes the root node's values. |
| */ |
| static void transfer_surpluses(struct list_head *surpluses, struct ioc_now *now) |
| { |
| LIST_HEAD(over_hwa); |
| LIST_HEAD(inner_walk); |
| struct ioc_gq *iocg, *tiocg, *root_iocg; |
| u32 after_sum, over_sum, over_target, gamma; |
| |
| /* |
| * It's pretty unlikely but possible for the total sum of |
| * hweight_after_donation's to be higher than WEIGHT_ONE, which will |
| * confuse the following calculations. If such condition is detected, |
| * scale down everyone over its full share equally to keep the sum below |
| * WEIGHT_ONE. |
| */ |
| after_sum = 0; |
| over_sum = 0; |
| list_for_each_entry(iocg, surpluses, surplus_list) { |
| u32 hwa; |
| |
| current_hweight(iocg, &hwa, NULL); |
| after_sum += iocg->hweight_after_donation; |
| |
| if (iocg->hweight_after_donation > hwa) { |
| over_sum += iocg->hweight_after_donation; |
| list_add(&iocg->walk_list, &over_hwa); |
| } |
| } |
| |
| if (after_sum >= WEIGHT_ONE) { |
| /* |
| * The delta should be deducted from the over_sum, calculate |
| * target over_sum value. |
| */ |
| u32 over_delta = after_sum - (WEIGHT_ONE - 1); |
| WARN_ON_ONCE(over_sum <= over_delta); |
| over_target = over_sum - over_delta; |
| } else { |
| over_target = 0; |
| } |
| |
| list_for_each_entry_safe(iocg, tiocg, &over_hwa, walk_list) { |
| if (over_target) |
| iocg->hweight_after_donation = |
| div_u64((u64)iocg->hweight_after_donation * |
| over_target, over_sum); |
| list_del_init(&iocg->walk_list); |
| } |
| |
| /* |
| * Build pre-order inner node walk list and prepare for donation |
| * adjustment calculations. |
| */ |
| list_for_each_entry(iocg, surpluses, surplus_list) { |
| iocg_build_inner_walk(iocg, &inner_walk); |
| } |
| |
| root_iocg = list_first_entry(&inner_walk, struct ioc_gq, walk_list); |
| WARN_ON_ONCE(root_iocg->level > 0); |
| |
| list_for_each_entry(iocg, &inner_walk, walk_list) { |
| iocg->child_adjusted_sum = 0; |
| iocg->hweight_donating = 0; |
| iocg->hweight_after_donation = 0; |
| } |
| |
| /* |
| * Propagate the donating budget (b_t) and after donation budget (b'_t) |
| * up the hierarchy. |
| */ |
| list_for_each_entry(iocg, surpluses, surplus_list) { |
| struct ioc_gq *parent = iocg->ancestors[iocg->level - 1]; |
| |
| parent->hweight_donating += iocg->hweight_donating; |
| parent->hweight_after_donation += iocg->hweight_after_donation; |
| } |
| |
| list_for_each_entry_reverse(iocg, &inner_walk, walk_list) { |
| if (iocg->level > 0) { |
| struct ioc_gq *parent = iocg->ancestors[iocg->level - 1]; |
| |
| parent->hweight_donating += iocg->hweight_donating; |
| parent->hweight_after_donation += iocg->hweight_after_donation; |
| } |
| } |
| |
| /* |
| * Calculate inner hwa's (b) and make sure the donation values are |
| * within the accepted ranges as we're doing low res calculations with |
| * roundups. |
| */ |
| list_for_each_entry(iocg, &inner_walk, walk_list) { |
| if (iocg->level) { |
| struct ioc_gq *parent = iocg->ancestors[iocg->level - 1]; |
| |
| iocg->hweight_active = DIV64_U64_ROUND_UP( |
| (u64)parent->hweight_active * iocg->active, |
| parent->child_active_sum); |
| |
| } |
| |
| iocg->hweight_donating = min(iocg->hweight_donating, |
| iocg->hweight_active); |
| iocg->hweight_after_donation = min(iocg->hweight_after_donation, |
| iocg->hweight_donating - 1); |
| if (WARN_ON_ONCE(iocg->hweight_active <= 1 || |
| iocg->hweight_donating <= 1 || |
| iocg->hweight_after_donation == 0)) { |
| pr_warn("iocg: invalid donation weights in "); |
| pr_cont_cgroup_path(iocg_to_blkg(iocg)->blkcg->css.cgroup); |
| pr_cont(": active=%u donating=%u after=%u\n", |
| iocg->hweight_active, iocg->hweight_donating, |
| iocg->hweight_after_donation); |
| } |
| } |
| |
| /* |
| * Calculate the global donation rate (gamma) - the rate to adjust |
| * non-donating budgets by. |
| * |
| * No need to use 64bit multiplication here as the first operand is |
| * guaranteed to be smaller than WEIGHT_ONE (1<<16). |
| * |
| * We know that there are beneficiary nodes and the sum of the donating |
| * hweights can't be whole; however, due to the round-ups during hweight |
| * calculations, root_iocg->hweight_donating might still end up equal to |
| * or greater than whole. Limit the range when calculating the divider. |
| * |
| * gamma = (1 - t_r') / (1 - t_r) |
| */ |
| gamma = DIV_ROUND_UP( |
| (WEIGHT_ONE - root_iocg->hweight_after_donation) * WEIGHT_ONE, |
| WEIGHT_ONE - min_t(u32, root_iocg->hweight_donating, WEIGHT_ONE - 1)); |
| |
| /* |
| * Calculate adjusted hwi, child_adjusted_sum and inuse for the inner |
| * nodes. |
| */ |
| list_for_each_entry(iocg, &inner_walk, walk_list) { |
| struct ioc_gq *parent; |
| u32 inuse, wpt, wptp; |
| u64 st, sf; |
| |
| if (iocg->level == 0) { |
| /* adjusted weight sum for 1st level: s' = s * b_pf / b'_pf */ |
| iocg->child_adjusted_sum = DIV64_U64_ROUND_UP( |
| iocg->child_active_sum * (WEIGHT_ONE - iocg->hweight_donating), |
| WEIGHT_ONE - iocg->hweight_after_donation); |
| continue; |
| } |
| |
| parent = iocg->ancestors[iocg->level - 1]; |
| |
| /* b' = gamma * b_f + b_t' */ |
| iocg->hweight_inuse = DIV64_U64_ROUND_UP( |
| (u64)gamma * (iocg->hweight_active - iocg->hweight_donating), |
| WEIGHT_ONE) + iocg->hweight_after_donation; |
| |
| /* w' = s' * b' / b'_p */ |
| inuse = DIV64_U64_ROUND_UP( |
| (u64)parent->child_adjusted_sum * iocg->hweight_inuse, |
| parent->hweight_inuse); |
| |
| /* adjusted weight sum for children: s' = s_f + s_t * w'_pt / w_pt */ |
| st = DIV64_U64_ROUND_UP( |
| iocg->child_active_sum * iocg->hweight_donating, |
| iocg->hweight_active); |
| sf = iocg->child_active_sum - st; |
| wpt = DIV64_U64_ROUND_UP( |
| (u64)iocg->active * iocg->hweight_donating, |
| iocg->hweight_active); |
| wptp = DIV64_U64_ROUND_UP( |
| (u64)inuse * iocg->hweight_after_donation, |
| iocg->hweight_inuse); |
| |
| iocg->child_adjusted_sum = sf + DIV64_U64_ROUND_UP(st * wptp, wpt); |
| } |
| |
| /* |
| * All inner nodes now have ->hweight_inuse and ->child_adjusted_sum and |
| * we can finally determine leaf adjustments. |
| */ |
| list_for_each_entry(iocg, surpluses, surplus_list) { |
| struct ioc_gq *parent = iocg->ancestors[iocg->level - 1]; |
| u32 inuse; |
| |
| /* |
| * In-debt iocgs participated in the donation calculation with |
| * the minimum target hweight_inuse. Configuring inuse |
| * accordingly would work fine but debt handling expects |
| * @iocg->inuse stay at the minimum and we don't wanna |
| * interfere. |
| */ |
| if (iocg->abs_vdebt) { |
| WARN_ON_ONCE(iocg->inuse > 1); |
| continue; |
| } |
| |
| /* w' = s' * b' / b'_p, note that b' == b'_t for donating leaves */ |
| inuse = DIV64_U64_ROUND_UP( |
| parent->child_adjusted_sum * iocg->hweight_after_donation, |
| parent->hweight_inuse); |
| |
| TRACE_IOCG_PATH(inuse_transfer, iocg, now, |
| iocg->inuse, inuse, |
| iocg->hweight_inuse, |
| iocg->hweight_after_donation); |
| |
| __propagate_weights(iocg, iocg->active, inuse, true, now); |
| } |
| |
| /* walk list should be dissolved after use */ |
| list_for_each_entry_safe(iocg, tiocg, &inner_walk, walk_list) |
| list_del_init(&iocg->walk_list); |
| } |
| |
| /* |
| * A low weight iocg can amass a large amount of debt, for example, when |
| * anonymous memory gets reclaimed aggressively. If the system has a lot of |
| * memory paired with a slow IO device, the debt can span multiple seconds or |
| * more. If there are no other subsequent IO issuers, the in-debt iocg may end |
| * up blocked paying its debt while the IO device is idle. |
| * |
| * The following protects against such cases. If the device has been |
| * sufficiently idle for a while, the debts are halved and delays are |
| * recalculated. |
| */ |
| static void ioc_forgive_debts(struct ioc *ioc, u64 usage_us_sum, int nr_debtors, |
| struct ioc_now *now) |
| { |
| struct ioc_gq *iocg; |
| u64 dur, usage_pct, nr_cycles; |
| |
| /* if no debtor, reset the cycle */ |
| if (!nr_debtors) { |
| ioc->dfgv_period_at = now->now; |
| ioc->dfgv_period_rem = 0; |
| ioc->dfgv_usage_us_sum = 0; |
| return; |
| } |
| |
| /* |
| * Debtors can pass through a lot of writes choking the device and we |
| * don't want to be forgiving debts while the device is struggling from |
| * write bursts. If we're missing latency targets, consider the device |
| * fully utilized. |
| */ |
| if (ioc->busy_level > 0) |
| usage_us_sum = max_t(u64, usage_us_sum, ioc->period_us); |
| |
| ioc->dfgv_usage_us_sum += usage_us_sum; |
| if (time_before64(now->now, ioc->dfgv_period_at + DFGV_PERIOD)) |
| return; |
| |
| /* |
| * At least DFGV_PERIOD has passed since the last period. Calculate the |
| * average usage and reset the period counters. |
| */ |
| dur = now->now - ioc->dfgv_period_at; |
| usage_pct = div64_u64(100 * ioc->dfgv_usage_us_sum, dur); |
| |
| ioc->dfgv_period_at = now->now; |
| ioc->dfgv_usage_us_sum = 0; |
| |
| /* if was too busy, reset everything */ |
| if (usage_pct > DFGV_USAGE_PCT) { |
| ioc->dfgv_period_rem = 0; |
| return; |
| } |
| |
| /* |
| * Usage is lower than threshold. Let's forgive some debts. Debt |
| * forgiveness runs off of the usual ioc timer but its period usually |
| * doesn't match ioc's. Compensate the difference by performing the |
| * reduction as many times as would fit in the duration since the last |
| * run and carrying over the left-over duration in @ioc->dfgv_period_rem |
| * - if ioc period is 75% of DFGV_PERIOD, one out of three consecutive |
| * reductions is doubled. |
| */ |
| nr_cycles = dur + ioc->dfgv_period_rem; |
| ioc->dfgv_period_rem = do_div(nr_cycles, DFGV_PERIOD); |
| |
| list_for_each_entry(iocg, &ioc->active_iocgs, active_list) { |
| u64 __maybe_unused old_debt, __maybe_unused old_delay; |
| |
| if (!iocg->abs_vdebt && !iocg->delay) |
| continue; |
| |
| spin_lock(&iocg->waitq.lock); |
| |
| old_debt = iocg->abs_vdebt; |
| old_delay = iocg->delay; |
| |
| if (iocg->abs_vdebt) |
| iocg->abs_vdebt = iocg->abs_vdebt >> nr_cycles ?: 1; |
| if (iocg->delay) |
| iocg->delay = iocg->delay >> nr_cycles ?: 1; |
| |
| iocg_kick_waitq(iocg, true, now); |
| |
| TRACE_IOCG_PATH(iocg_forgive_debt, iocg, now, usage_pct, |
| old_debt, iocg->abs_vdebt, |
| old_delay, iocg->delay); |
| |
| spin_unlock(&iocg->waitq.lock); |
| } |
| } |
| |
| /* |
| * Check the active iocgs' state to avoid oversleeping and deactive |
| * idle iocgs. |
| * |
| * Since waiters determine the sleep durations based on the vrate |
| * they saw at the time of sleep, if vrate has increased, some |
| * waiters could be sleeping for too long. Wake up tardy waiters |
| * which should have woken up in the last period and expire idle |
| * iocgs. |
| */ |
| static int ioc_check_iocgs(struct ioc *ioc, struct ioc_now *now) |
| { |
| int nr_debtors = 0; |
| struct ioc_gq *iocg, *tiocg; |
| |
| list_for_each_entry_safe(iocg, tiocg, &ioc->active_iocgs, active_list) { |
| if (!waitqueue_active(&iocg->waitq) && !iocg->abs_vdebt && |
| !iocg->delay && !iocg_is_idle(iocg)) |
| continue; |
| |
| spin_lock(&iocg->waitq.lock); |
| |
| /* flush wait and indebt stat deltas */ |
| if (iocg->wait_since) { |
| iocg->stat.wait_us += now->now - iocg->wait_since; |
| iocg->wait_since = now->now; |
| } |
| if (iocg->indebt_since) { |
| iocg->stat.indebt_us += |
| now->now - iocg->indebt_since; |
| iocg->indebt_since = now->now; |
| } |
| if (iocg->indelay_since) { |
| iocg->stat.indelay_us += |
| now->now - iocg->indelay_since; |
| iocg->indelay_since = now->now; |
| } |
| |
| if (waitqueue_active(&iocg->waitq) || iocg->abs_vdebt || |
| iocg->delay) { |
| /* might be oversleeping vtime / hweight changes, kick */ |
| iocg_kick_waitq(iocg, true, now); |
| if (iocg->abs_vdebt || iocg->delay) |
| nr_debtors++; |
| } else if (iocg_is_idle(iocg)) { |
| /* no waiter and idle, deactivate */ |
| u64 vtime = atomic64_read(&iocg->vtime); |
| s64 excess; |
| |
| /* |
| * @iocg has been inactive for a full duration and will |
| * have a high budget. Account anything above target as |
| * error and throw away. On reactivation, it'll start |
| * with the target budget. |
| */ |
| excess = now->vnow - vtime - ioc->margins.target; |
| if (excess > 0) { |
| u32 old_hwi; |
| |
| current_hweight(iocg, NULL, &old_hwi); |
| ioc->vtime_err -= div64_u64(excess * old_hwi, |
| WEIGHT_ONE); |
| } |
| |
| TRACE_IOCG_PATH(iocg_idle, iocg, now, |
| atomic64_read(&iocg->active_period), |
| atomic64_read(&ioc->cur_period), vtime); |
| __propagate_weights(iocg, 0, 0, false, now); |
| list_del_init(&iocg->active_list); |
| } |
| |
| spin_unlock(&iocg->waitq.lock); |
| } |
| |
| commit_weights(ioc); |
| return nr_debtors; |
| } |
| |
| static void ioc_timer_fn(struct timer_list *timer) |
| { |
| struct ioc *ioc = container_of(timer, struct ioc, timer); |
| struct ioc_gq *iocg, *tiocg; |
| struct ioc_now now; |
| LIST_HEAD(surpluses); |
| int nr_debtors, nr_shortages = 0, nr_lagging = 0; |
| u64 usage_us_sum = 0; |
| u32 ppm_rthr; |
| u32 ppm_wthr; |
| u32 missed_ppm[2], rq_wait_pct; |
| u64 period_vtime; |
| int prev_busy_level; |
| |
| /* how were the latencies during the period? */ |
| ioc_lat_stat(ioc, missed_ppm, &rq_wait_pct); |
| |
| /* take care of active iocgs */ |
| spin_lock_irq(&ioc->lock); |
| |
| ppm_rthr = MILLION - ioc->params.qos[QOS_RPPM]; |
| ppm_wthr = MILLION - ioc->params.qos[QOS_WPPM]; |
| ioc_now(ioc, &now); |
| |
| period_vtime = now.vnow - ioc->period_at_vtime; |
| if (WARN_ON_ONCE(!period_vtime)) { |
| spin_unlock_irq(&ioc->lock); |
| return; |
| } |
| |
| nr_debtors = ioc_check_iocgs(ioc, &now); |
| |
| /* |
| * Wait and indebt stat are flushed above and the donation calculation |
| * below needs updated usage stat. Let's bring stat up-to-date. |
| */ |
| iocg_flush_stat(&ioc->active_iocgs, &now); |
| |
| /* calc usage and see whether some weights need to be moved around */ |
| list_for_each_entry(iocg, &ioc->active_iocgs, active_list) { |
| u64 vdone, vtime, usage_us; |
| u32 hw_active, hw_inuse; |
| |
| /* |
| * Collect unused and wind vtime closer to vnow to prevent |
| * iocgs from accumulating a large amount of budget. |
| */ |
| vdone = atomic64_read(&iocg->done_vtime); |
| vtime = atomic64_read(&iocg->vtime); |
| current_hweight(iocg, &hw_active, &hw_inuse); |
| |
| /* |
| * Latency QoS detection doesn't account for IOs which are |
| * in-flight for longer than a period. Detect them by |
| * comparing vdone against period start. If lagging behind |
| * IOs from past periods, don't increase vrate. |
| */ |
| if ((ppm_rthr != MILLION || ppm_wthr != MILLION) && |
| !atomic_read(&iocg_to_blkg(iocg)->use_delay) && |
| time_after64(vtime, vdone) && |
| time_after64(vtime, now.vnow - |
| MAX_LAGGING_PERIODS * period_vtime) && |
| time_before64(vdone, now.vnow - period_vtime)) |
| nr_lagging++; |
| |
| /* |
| * Determine absolute usage factoring in in-flight IOs to avoid |
| * high-latency completions appearing as idle. |
| */ |
| usage_us = iocg->usage_delta_us; |
| usage_us_sum += usage_us; |
| |
| /* see whether there's surplus vtime */ |
| WARN_ON_ONCE(!list_empty(&iocg->surplus_list)); |
| if (hw_inuse < hw_active || |
| (!waitqueue_active(&iocg->waitq) && |
| time_before64(vtime, now.vnow - ioc->margins.low))) { |
| u32 hwa, old_hwi, hwm, new_hwi, usage; |
| u64 usage_dur; |
| |
| if (vdone != vtime) { |
| u64 inflight_us = DIV64_U64_ROUND_UP( |
| cost_to_abs_cost(vtime - vdone, hw_inuse), |
| ioc->vtime_base_rate); |
| |
| usage_us = max(usage_us, inflight_us); |
| } |
| |
| /* convert to hweight based usage ratio */ |
| if (time_after64(iocg->activated_at, ioc->period_at)) |
| usage_dur = max_t(u64, now.now - iocg->activated_at, 1); |
| else |
| usage_dur = max_t(u64, now.now - ioc->period_at, 1); |
| |
| usage = clamp_t(u32, |
| DIV64_U64_ROUND_UP(usage_us * WEIGHT_ONE, |
| usage_dur), |
| 1, WEIGHT_ONE); |
| |
| /* |
| * Already donating or accumulated enough to start. |
| * Determine the donation amount. |
| */ |
| current_hweight(iocg, &hwa, &old_hwi); |
| hwm = current_hweight_max(iocg); |
| new_hwi = hweight_after_donation(iocg, old_hwi, hwm, |
| usage, &now); |
| /* |
| * Donation calculation assumes hweight_after_donation |
| * to be positive, a condition that a donor w/ hwa < 2 |
| * can't meet. Don't bother with donation if hwa is |
| * below 2. It's not gonna make a meaningful difference |
| * anyway. |
| */ |
| if (new_hwi < hwm && hwa >= 2) { |
| iocg->hweight_donating = hwa; |
| iocg->hweight_after_donation = new_hwi; |
| list_add(&iocg->surplus_list, &surpluses); |
| } else if (!iocg->abs_vdebt) { |
| /* |
| * @iocg doesn't have enough to donate. Reset |
| * its inuse to active. |
| * |
| * Don't reset debtors as their inuse's are |
| * owned by debt handling. This shouldn't affect |
| * donation calculuation in any meaningful way |
| * as @iocg doesn't have a meaningful amount of |
| * share anyway. |
| */ |
| TRACE_IOCG_PATH(inuse_shortage, iocg, &now, |
| iocg->inuse, iocg->active, |
| iocg->hweight_inuse, new_hwi); |
| |
| __propagate_weights(iocg, iocg->active, |
| iocg->active, true, &now); |
| nr_shortages++; |
| } |
| } else { |
| /* genuinely short on vtime */ |
| nr_shortages++; |
| } |
| } |
| |
| if (!list_empty(&surpluses) && nr_shortages) |
| transfer_surpluses(&surpluses, &now); |
| |
| commit_weights(ioc); |
| |
| /* surplus list should be dissolved after use */ |
| list_for_each_entry_safe(iocg, tiocg, &surpluses, surplus_list) |
| list_del_init(&iocg->surplus_list); |
| |
| /* |
| * If q is getting clogged or we're missing too much, we're issuing |
| * too much IO and should lower vtime rate. If we're not missing |
| * and experiencing shortages but not surpluses, we're too stingy |
| * and should increase vtime rate. |
| */ |
| prev_busy_level = ioc->busy_level; |
| if (rq_wait_pct > RQ_WAIT_BUSY_PCT || |
| missed_ppm[READ] > ppm_rthr || |
| missed_ppm[WRITE] > ppm_wthr) { |
| /* clearly missing QoS targets, slow down vrate */ |
| ioc->busy_level = max(ioc->busy_level, 0); |
| ioc->busy_level++; |
| } else if (rq_wait_pct <= RQ_WAIT_BUSY_PCT * UNBUSY_THR_PCT / 100 && |
| missed_ppm[READ] <= ppm_rthr * UNBUSY_THR_PCT / 100 && |
| missed_ppm[WRITE] <= ppm_wthr * UNBUSY_THR_PCT / 100) { |
| /* QoS targets are being met with >25% margin */ |
| if (nr_shortages) { |
| /* |
| * We're throttling while the device has spare |
| * capacity. If vrate was being slowed down, stop. |
| */ |
| ioc->busy_level = min(ioc->busy_level, 0); |
| |
| /* |
| * If there are IOs spanning multiple periods, wait |
| * them out before pushing the device harder. |
| */ |
| if (!nr_lagging) |
| ioc->busy_level--; |
| } else { |
| /* |
| * Nobody is being throttled and the users aren't |
| * issuing enough IOs to saturate the device. We |
| * simply don't know how close the device is to |
| * saturation. Coast. |
| */ |
| ioc->busy_level = 0; |
| } |
| } else { |
| /* inside the hysterisis margin, we're good */ |
| ioc->busy_level = 0; |
| } |
| |
| ioc->busy_level = clamp(ioc->busy_level, -1000, 1000); |
| |
| ioc_adjust_base_vrate(ioc, rq_wait_pct, nr_lagging, nr_shortages, |
| prev_busy_level, missed_ppm); |
| |
| ioc_refresh_params(ioc, false); |
| |
| ioc_forgive_debts(ioc, usage_us_sum, nr_debtors, &now); |
| |
| /* |
| * This period is done. Move onto the next one. If nothing's |
| * going on with the device, stop the timer. |
| */ |
| atomic64_inc(&ioc->cur_period); |
| |
| if (ioc->running != IOC_STOP) { |
| if (!list_empty(&ioc->active_iocgs)) { |
| ioc_start_period(ioc, &now); |
| } else { |
| ioc->busy_level = 0; |
| ioc->vtime_err = 0; |
| ioc->running = IOC_IDLE; |
| } |
| |
| ioc_refresh_vrate(ioc, &now); |
| } |
| |
| spin_unlock_irq(&ioc->lock); |
| } |
| |
| static u64 adjust_inuse_and_calc_cost(struct ioc_gq *iocg, u64 vtime, |
| u64 abs_cost, struct ioc_now *now) |
| { |
| struct ioc *ioc = iocg->ioc; |
| struct ioc_margins *margins = &ioc->margins; |
| u32 __maybe_unused old_inuse = iocg->inuse, __maybe_unused old_hwi; |
| u32 hwi, adj_step; |
| s64 margin; |
| u64 cost, new_inuse; |
| unsigned long flags; |
| |
| current_hweight(iocg, NULL, &hwi); |
| old_hwi = hwi; |
| cost = abs_cost_to_cost(abs_cost, hwi); |
| margin = now->vnow - vtime - cost; |
| |
| /* debt handling owns inuse for debtors */ |
| if (iocg->abs_vdebt) |
| return cost; |
| |
| /* |
| * We only increase inuse during period and do so if the margin has |
| * deteriorated since the previous adjustment. |
| */ |
| if (margin >= iocg->saved_margin || margin >= margins->low || |
| iocg->inuse == iocg->active) |
| return cost; |
| |
| spin_lock_irqsave(&ioc->lock, flags); |
| |
| /* we own inuse only when @iocg is in the normal active state */ |
| if (iocg->abs_vdebt || list_empty(&iocg->active_list)) { |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| return cost; |
| } |
| |
| /* |
| * Bump up inuse till @abs_cost fits in the existing budget. |
| * adj_step must be determined after acquiring ioc->lock - we might |
| * have raced and lost to another thread for activation and could |
| * be reading 0 iocg->active before ioc->lock which will lead to |
| * infinite loop. |
| */ |
| new_inuse = iocg->inuse; |
| adj_step = DIV_ROUND_UP(iocg->active * INUSE_ADJ_STEP_PCT, 100); |
| do { |
| new_inuse = new_inuse + adj_step; |
| propagate_weights(iocg, iocg->active, new_inuse, true, now); |
| current_hweight(iocg, NULL, &hwi); |
| cost = abs_cost_to_cost(abs_cost, hwi); |
| } while (time_after64(vtime + cost, now->vnow) && |
| iocg->inuse != iocg->active); |
| |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| |
| TRACE_IOCG_PATH(inuse_adjust, iocg, now, |
| old_inuse, iocg->inuse, old_hwi, hwi); |
| |
| return cost; |
| } |
| |
| static void calc_vtime_cost_builtin(struct bio *bio, struct ioc_gq *iocg, |
| bool is_merge, u64 *costp) |
| { |
| struct ioc *ioc = iocg->ioc; |
| u64 coef_seqio, coef_randio, coef_page; |
| u64 pages = max_t(u64, bio_sectors(bio) >> IOC_SECT_TO_PAGE_SHIFT, 1); |
| u64 seek_pages = 0; |
| u64 cost = 0; |
| |
| /* Can't calculate cost for empty bio */ |
| if (!bio->bi_iter.bi_size) |
| goto out; |
| |
| switch (bio_op(bio)) { |
| case REQ_OP_READ: |
| coef_seqio = ioc->params.lcoefs[LCOEF_RSEQIO]; |
| coef_randio = ioc->params.lcoefs[LCOEF_RRANDIO]; |
| coef_page = ioc->params.lcoefs[LCOEF_RPAGE]; |
| break; |
| case REQ_OP_WRITE: |
| coef_seqio = ioc->params.lcoefs[LCOEF_WSEQIO]; |
| coef_randio = ioc->params.lcoefs[LCOEF_WRANDIO]; |
| coef_page = ioc->params.lcoefs[LCOEF_WPAGE]; |
| break; |
| default: |
| goto out; |
| } |
| |
| if (iocg->cursor) { |
| seek_pages = abs(bio->bi_iter.bi_sector - iocg->cursor); |
| seek_pages >>= IOC_SECT_TO_PAGE_SHIFT; |
| } |
| |
| if (!is_merge) { |
| if (seek_pages > LCOEF_RANDIO_PAGES) { |
| cost += coef_randio; |
| } else { |
| cost += coef_seqio; |
| } |
| } |
| cost += pages * coef_page; |
| out: |
| *costp = cost; |
| } |
| |
| static u64 calc_vtime_cost(struct bio *bio, struct ioc_gq *iocg, bool is_merge) |
| { |
| u64 cost; |
| |
| calc_vtime_cost_builtin(bio, iocg, is_merge, &cost); |
| return cost; |
| } |
| |
| static void calc_size_vtime_cost_builtin(struct request *rq, struct ioc *ioc, |
| u64 *costp) |
| { |
| unsigned int pages = blk_rq_stats_sectors(rq) >> IOC_SECT_TO_PAGE_SHIFT; |
| |
| switch (req_op(rq)) { |
| case REQ_OP_READ: |
| *costp = pages * ioc->params.lcoefs[LCOEF_RPAGE]; |
| break; |
| case REQ_OP_WRITE: |
| *costp = pages * ioc->params.lcoefs[LCOEF_WPAGE]; |
| break; |
| default: |
| *costp = 0; |
| } |
| } |
| |
| static u64 calc_size_vtime_cost(struct request *rq, struct ioc *ioc) |
| { |
| u64 cost; |
| |
| calc_size_vtime_cost_builtin(rq, ioc, &cost); |
| return cost; |
| } |
| |
| static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio) |
| { |
| struct blkcg_gq *blkg = bio->bi_blkg; |
| struct ioc *ioc = rqos_to_ioc(rqos); |
| struct ioc_gq *iocg = blkg_to_iocg(blkg); |
| struct ioc_now now; |
| struct iocg_wait wait; |
| u64 abs_cost, cost, vtime; |
| bool use_debt, ioc_locked; |
| unsigned long flags; |
| |
| /* bypass IOs if disabled, still initializing, or for root cgroup */ |
| if (!ioc->enabled || !iocg || !iocg->level) |
| return; |
| |
| /* calculate the absolute vtime cost */ |
| abs_cost = calc_vtime_cost(bio, iocg, false); |
| if (!abs_cost) |
| return; |
| |
| if (!iocg_activate(iocg, &now)) |
| return; |
| |
| iocg->cursor = bio_end_sector(bio); |
| vtime = atomic64_read(&iocg->vtime); |
| cost = adjust_inuse_and_calc_cost(iocg, vtime, abs_cost, &now); |
| |
| /* |
| * If no one's waiting and within budget, issue right away. The |
| * tests are racy but the races aren't systemic - we only miss once |
| * in a while which is fine. |
| */ |
| if (!waitqueue_active(&iocg->waitq) && !iocg->abs_vdebt && |
| time_before_eq64(vtime + cost, now.vnow)) { |
| iocg_commit_bio(iocg, bio, abs_cost, cost); |
| return; |
| } |
| |
| /* |
| * We're over budget. This can be handled in two ways. IOs which may |
| * cause priority inversions are punted to @ioc->aux_iocg and charged as |
| * debt. Otherwise, the issuer is blocked on @iocg->waitq. Debt handling |
| * requires @ioc->lock, waitq handling @iocg->waitq.lock. Determine |
| * whether debt handling is needed and acquire locks accordingly. |
| */ |
| use_debt = bio_issue_as_root_blkg(bio) || fatal_signal_pending(current); |
| ioc_locked = use_debt || READ_ONCE(iocg->abs_vdebt); |
| retry_lock: |
| iocg_lock(iocg, ioc_locked, &flags); |
| |
| /* |
| * @iocg must stay activated for debt and waitq handling. Deactivation |
| * is synchronized against both ioc->lock and waitq.lock and we won't |
| * get deactivated as long as we're waiting or has debt, so we're good |
| * if we're activated here. In the unlikely cases that we aren't, just |
| * issue the IO. |
| */ |
| if (unlikely(list_empty(&iocg->active_list))) { |
| iocg_unlock(iocg, ioc_locked, &flags); |
| iocg_commit_bio(iocg, bio, abs_cost, cost); |
| return; |
| } |
| |
| /* |
| * We're over budget. If @bio has to be issued regardless, remember |
| * the abs_cost instead of advancing vtime. iocg_kick_waitq() will pay |
| * off the debt before waking more IOs. |
| * |
| * This way, the debt is continuously paid off each period with the |
| * actual budget available to the cgroup. If we just wound vtime, we |
| * would incorrectly use the current hw_inuse for the entire amount |
| * which, for example, can lead to the cgroup staying blocked for a |
| * long time even with substantially raised hw_inuse. |
| * |
| * An iocg with vdebt should stay online so that the timer can keep |
| * deducting its vdebt and [de]activate use_delay mechanism |
| * accordingly. We don't want to race against the timer trying to |
| * clear them and leave @iocg inactive w/ dangling use_delay heavily |
| * penalizing the cgroup and its descendants. |
| */ |
| if (use_debt) { |
| iocg_incur_debt(iocg, abs_cost, &now); |
| if (iocg_kick_delay(iocg, &now)) |
| blkcg_schedule_throttle(rqos->disk, |
| (bio->bi_opf & REQ_SWAP) == REQ_SWAP); |
| iocg_unlock(iocg, ioc_locked, &flags); |
| return; |
| } |
| |
| /* guarantee that iocgs w/ waiters have maximum inuse */ |
| if (!iocg->abs_vdebt && iocg->inuse != iocg->active) { |
| if (!ioc_locked) { |
| iocg_unlock(iocg, false, &flags); |
| ioc_locked = true; |
| goto retry_lock; |
| } |
| propagate_weights(iocg, iocg->active, iocg->active, true, |
| &now); |
| } |
| |
| /* |
| * Append self to the waitq and schedule the wakeup timer if we're |
| * the first waiter. The timer duration is calculated based on the |
| * current vrate. vtime and hweight changes can make it too short |
| * or too long. Each wait entry records the absolute cost it's |
| * waiting for to allow re-evaluation using a custom wait entry. |
| * |
| * If too short, the timer simply reschedules itself. If too long, |
| * the period timer will notice and trigger wakeups. |
| * |
| * All waiters are on iocg->waitq and the wait states are |
| * synchronized using waitq.lock. |
| */ |
| init_waitqueue_func_entry(&wait.wait, iocg_wake_fn); |
| wait.wait.private = current; |
| wait.bio = bio; |
| wait.abs_cost = abs_cost; |
| wait.committed = false; /* will be set true by waker */ |
| |
| __add_wait_queue_entry_tail(&iocg->waitq, &wait.wait); |
| iocg_kick_waitq(iocg, ioc_locked, &now); |
| |
| iocg_unlock(iocg, ioc_locked, &flags); |
| |
| while (true) { |
| set_current_state(TASK_UNINTERRUPTIBLE); |
| if (wait.committed) |
| break; |
| io_schedule(); |
| } |
| |
| /* waker already committed us, proceed */ |
| finish_wait(&iocg->waitq, &wait.wait); |
| } |
| |
| static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq, |
| struct bio *bio) |
| { |
| struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg); |
| struct ioc *ioc = rqos_to_ioc(rqos); |
| sector_t bio_end = bio_end_sector(bio); |
| struct ioc_now now; |
| u64 vtime, abs_cost, cost; |
| unsigned long flags; |
| |
| /* bypass if disabled, still initializing, or for root cgroup */ |
| if (!ioc->enabled || !iocg || !iocg->level) |
| return; |
| |
| abs_cost = calc_vtime_cost(bio, iocg, true); |
| if (!abs_cost) |
| return; |
| |
| ioc_now(ioc, &now); |
| |
| vtime = atomic64_read(&iocg->vtime); |
| cost = adjust_inuse_and_calc_cost(iocg, vtime, abs_cost, &now); |
| |
| /* update cursor if backmerging into the request at the cursor */ |
| if (blk_rq_pos(rq) < bio_end && |
| blk_rq_pos(rq) + blk_rq_sectors(rq) == iocg->cursor) |
| iocg->cursor = bio_end; |
| |
| /* |
| * Charge if there's enough vtime budget and the existing request has |
| * cost assigned. |
| */ |
| if (rq->bio && rq->bio->bi_iocost_cost && |
| time_before_eq64(atomic64_read(&iocg->vtime) + cost, now.vnow)) { |
| iocg_commit_bio(iocg, bio, abs_cost, cost); |
| return; |
| } |
| |
| /* |
| * Otherwise, account it as debt if @iocg is online, which it should |
| * be for the vast majority of cases. See debt handling in |
| * ioc_rqos_throttle() for details. |
| */ |
| spin_lock_irqsave(&ioc->lock, flags); |
| spin_lock(&iocg->waitq.lock); |
| |
| if (likely(!list_empty(&iocg->active_list))) { |
| iocg_incur_debt(iocg, abs_cost, &now); |
| if (iocg_kick_delay(iocg, &now)) |
| blkcg_schedule_throttle(rqos->disk, |
| (bio->bi_opf & REQ_SWAP) == REQ_SWAP); |
| } else { |
| iocg_commit_bio(iocg, bio, abs_cost, cost); |
| } |
| |
| spin_unlock(&iocg->waitq.lock); |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| } |
| |
| static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio) |
| { |
| struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg); |
| |
| if (iocg && bio->bi_iocost_cost) |
| atomic64_add(bio->bi_iocost_cost, &iocg->done_vtime); |
| } |
| |
| static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq) |
| { |
| struct ioc *ioc = rqos_to_ioc(rqos); |
| struct ioc_pcpu_stat *ccs; |
| u64 on_q_ns, rq_wait_ns, size_nsec; |
| int pidx, rw; |
| |
| if (!ioc->enabled || !rq->alloc_time_ns || !rq->start_time_ns) |
| return; |
| |
| switch (req_op(rq)) { |
| case REQ_OP_READ: |
| pidx = QOS_RLAT; |
| rw = READ; |
| break; |
| case REQ_OP_WRITE: |
| pidx = QOS_WLAT; |
| rw = WRITE; |
| break; |
| default: |
| return; |
| } |
| |
| on_q_ns = blk_time_get_ns() - rq->alloc_time_ns; |
| rq_wait_ns = rq->start_time_ns - rq->alloc_time_ns; |
| size_nsec = div64_u64(calc_size_vtime_cost(rq, ioc), VTIME_PER_NSEC); |
| |
| ccs = get_cpu_ptr(ioc->pcpu_stat); |
| |
| if (on_q_ns <= size_nsec || |
| on_q_ns - size_nsec <= ioc->params.qos[pidx] * NSEC_PER_USEC) |
| local_inc(&ccs->missed[rw].nr_met); |
| else |
| local_inc(&ccs->missed[rw].nr_missed); |
| |
| local64_add(rq_wait_ns, &ccs->rq_wait_ns); |
| |
| put_cpu_ptr(ccs); |
| } |
| |
| static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos) |
| { |
| struct ioc *ioc = rqos_to_ioc(rqos); |
| |
| spin_lock_irq(&ioc->lock); |
| ioc_refresh_params(ioc, false); |
| spin_unlock_irq(&ioc->lock); |
| } |
| |
| static void ioc_rqos_exit(struct rq_qos *rqos) |
| { |
| struct ioc *ioc = rqos_to_ioc(rqos); |
| |
| blkcg_deactivate_policy(rqos->disk, &blkcg_policy_iocost); |
| |
| spin_lock_irq(&ioc->lock); |
| ioc->running = IOC_STOP; |
| spin_unlock_irq(&ioc->lock); |
| |
| timer_shutdown_sync(&ioc->timer); |
| free_percpu(ioc->pcpu_stat); |
| kfree(ioc); |
| } |
| |
| static const struct rq_qos_ops ioc_rqos_ops = { |
| .throttle = ioc_rqos_throttle, |
| .merge = ioc_rqos_merge, |
| .done_bio = ioc_rqos_done_bio, |
| .done = ioc_rqos_done, |
| .queue_depth_changed = ioc_rqos_queue_depth_changed, |
| .exit = ioc_rqos_exit, |
| }; |
| |
| static int blk_iocost_init(struct gendisk *disk) |
| { |
| struct ioc *ioc; |
| int i, cpu, ret; |
| |
| ioc = kzalloc(sizeof(*ioc), GFP_KERNEL); |
| if (!ioc) |
| return -ENOMEM; |
| |
| ioc->pcpu_stat = alloc_percpu(struct ioc_pcpu_stat); |
| if (!ioc->pcpu_stat) { |
| kfree(ioc); |
| return -ENOMEM; |
| } |
| |
| for_each_possible_cpu(cpu) { |
| struct ioc_pcpu_stat *ccs = per_cpu_ptr(ioc->pcpu_stat, cpu); |
| |
| for (i = 0; i < ARRAY_SIZE(ccs->missed); i++) { |
| local_set(&ccs->missed[i].nr_met, 0); |
| local_set(&ccs->missed[i].nr_missed, 0); |
| } |
| local64_set(&ccs->rq_wait_ns, 0); |
| } |
| |
| spin_lock_init(&ioc->lock); |
| timer_setup(&ioc->timer, ioc_timer_fn, 0); |
| INIT_LIST_HEAD(&ioc->active_iocgs); |
| |
| ioc->running = IOC_IDLE; |
| ioc->vtime_base_rate = VTIME_PER_USEC; |
| atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC); |
| seqcount_spinlock_init(&ioc->period_seqcount, &ioc->lock); |
| ioc->period_at = ktime_to_us(blk_time_get()); |
| atomic64_set(&ioc->cur_period, 0); |
| atomic_set(&ioc->hweight_gen, 0); |
| |
| spin_lock_irq(&ioc->lock); |
| ioc->autop_idx = AUTOP_INVALID; |
| ioc_refresh_params_disk(ioc, true, disk); |
| spin_unlock_irq(&ioc->lock); |
| |
| /* |
| * rqos must be added before activation to allow ioc_pd_init() to |
| * lookup the ioc from q. This means that the rqos methods may get |
| * called before policy activation completion, can't assume that the |
| * target bio has an iocg associated and need to test for NULL iocg. |
| */ |
| ret = rq_qos_add(&ioc->rqos, disk, RQ_QOS_COST, &ioc_rqos_ops); |
| if (ret) |
| goto err_free_ioc; |
| |
| ret = blkcg_activate_policy(disk, &blkcg_policy_iocost); |
| if (ret) |
| goto err_del_qos; |
| return 0; |
| |
| err_del_qos: |
| rq_qos_del(&ioc->rqos); |
| err_free_ioc: |
| free_percpu(ioc->pcpu_stat); |
| kfree(ioc); |
| return ret; |
| } |
| |
| static struct blkcg_policy_data *ioc_cpd_alloc(gfp_t gfp) |
| { |
| struct ioc_cgrp *iocc; |
| |
| iocc = kzalloc(sizeof(struct ioc_cgrp), gfp); |
| if (!iocc) |
| return NULL; |
| |
| iocc->dfl_weight = CGROUP_WEIGHT_DFL * WEIGHT_ONE; |
| return &iocc->cpd; |
| } |
| |
| static void ioc_cpd_free(struct blkcg_policy_data *cpd) |
| { |
| kfree(container_of(cpd, struct ioc_cgrp, cpd)); |
| } |
| |
| static struct blkg_policy_data *ioc_pd_alloc(struct gendisk *disk, |
| struct blkcg *blkcg, gfp_t gfp) |
| { |
| int levels = blkcg->css.cgroup->level + 1; |
| struct ioc_gq *iocg; |
| |
| iocg = kzalloc_node(struct_size(iocg, ancestors, levels), gfp, |
| disk->node_id); |
| if (!iocg) |
| return NULL; |
| |
| iocg->pcpu_stat = alloc_percpu_gfp(struct iocg_pcpu_stat, gfp); |
| if (!iocg->pcpu_stat) { |
| kfree(iocg); |
| return NULL; |
| } |
| |
| return &iocg->pd; |
| } |
| |
| static void ioc_pd_init(struct blkg_policy_data *pd) |
| { |
| struct ioc_gq *iocg = pd_to_iocg(pd); |
| struct blkcg_gq *blkg = pd_to_blkg(&iocg->pd); |
| struct ioc *ioc = q_to_ioc(blkg->q); |
| struct ioc_now now; |
| struct blkcg_gq *tblkg; |
| unsigned long flags; |
| |
| ioc_now(ioc, &now); |
| |
| iocg->ioc = ioc; |
| atomic64_set(&iocg->vtime, now.vnow); |
| atomic64_set(&iocg->done_vtime, now.vnow); |
| atomic64_set(&iocg->active_period, atomic64_read(&ioc->cur_period)); |
| INIT_LIST_HEAD(&iocg->active_list); |
| INIT_LIST_HEAD(&iocg->walk_list); |
| INIT_LIST_HEAD(&iocg->surplus_list); |
| iocg->hweight_active = WEIGHT_ONE; |
| iocg->hweight_inuse = WEIGHT_ONE; |
| |
| init_waitqueue_head(&iocg->waitq); |
| hrtimer_init(&iocg->waitq_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); |
| iocg->waitq_timer.function = iocg_waitq_timer_fn; |
| |
| iocg->level = blkg->blkcg->css.cgroup->level; |
| |
| for (tblkg = blkg; tblkg; tblkg = tblkg->parent) { |
| struct ioc_gq *tiocg = blkg_to_iocg(tblkg); |
| iocg->ancestors[tiocg->level] = tiocg; |
| } |
| |
| spin_lock_irqsave(&ioc->lock, flags); |
| weight_updated(iocg, &now); |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| } |
| |
| static void ioc_pd_free(struct blkg_policy_data *pd) |
| { |
| struct ioc_gq *iocg = pd_to_iocg(pd); |
| struct ioc *ioc = iocg->ioc; |
| unsigned long flags; |
| |
| if (ioc) { |
| spin_lock_irqsave(&ioc->lock, flags); |
| |
| if (!list_empty(&iocg->active_list)) { |
| struct ioc_now now; |
| |
| ioc_now(ioc, &now); |
| propagate_weights(iocg, 0, 0, false, &now); |
| list_del_init(&iocg->active_list); |
| } |
| |
| WARN_ON_ONCE(!list_empty(&iocg->walk_list)); |
| WARN_ON_ONCE(!list_empty(&iocg->surplus_list)); |
| |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| |
| hrtimer_cancel(&iocg->waitq_timer); |
| } |
| free_percpu(iocg->pcpu_stat); |
| kfree(iocg); |
| } |
| |
| static void ioc_pd_stat(struct blkg_policy_data *pd, struct seq_file *s) |
| { |
| struct ioc_gq *iocg = pd_to_iocg(pd); |
| struct ioc *ioc = iocg->ioc; |
| |
| if (!ioc->enabled) |
| return; |
| |
| if (iocg->level == 0) { |
| unsigned vp10k = DIV64_U64_ROUND_CLOSEST( |
| ioc->vtime_base_rate * 10000, |
| VTIME_PER_USEC); |
| seq_printf(s, " cost.vrate=%u.%02u", vp10k / 100, vp10k % 100); |
| } |
| |
| seq_printf(s, " cost.usage=%llu", iocg->last_stat.usage_us); |
| |
| if (blkcg_debug_stats) |
| seq_printf(s, " cost.wait=%llu cost.indebt=%llu cost.indelay=%llu", |
| iocg->last_stat.wait_us, |
| iocg->last_stat.indebt_us, |
| iocg->last_stat.indelay_us); |
| } |
| |
| static u64 ioc_weight_prfill(struct seq_file *sf, struct blkg_policy_data *pd, |
| int off) |
| { |
| const char *dname = blkg_dev_name(pd->blkg); |
| struct ioc_gq *iocg = pd_to_iocg(pd); |
| |
| if (dname && iocg->cfg_weight) |
| seq_printf(sf, "%s %u\n", dname, iocg->cfg_weight / WEIGHT_ONE); |
| return 0; |
| } |
| |
| |
| static int ioc_weight_show(struct seq_file *sf, void *v) |
| { |
| struct blkcg *blkcg = css_to_blkcg(seq_css(sf)); |
| struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg); |
| |
| seq_printf(sf, "default %u\n", iocc->dfl_weight / WEIGHT_ONE); |
| blkcg_print_blkgs(sf, blkcg, ioc_weight_prfill, |
| &blkcg_policy_iocost, seq_cft(sf)->private, false); |
| return 0; |
| } |
| |
| static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf, |
| size_t nbytes, loff_t off) |
| { |
| struct blkcg *blkcg = css_to_blkcg(of_css(of)); |
| struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg); |
| struct blkg_conf_ctx ctx; |
| struct ioc_now now; |
| struct ioc_gq *iocg; |
| u32 v; |
| int ret; |
| |
| if (!strchr(buf, ':')) { |
| struct blkcg_gq *blkg; |
| |
| if (!sscanf(buf, "default %u", &v) && !sscanf(buf, "%u", &v)) |
| return -EINVAL; |
| |
| if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX) |
| return -EINVAL; |
| |
| spin_lock_irq(&blkcg->lock); |
| iocc->dfl_weight = v * WEIGHT_ONE; |
| hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) { |
| struct ioc_gq *iocg = blkg_to_iocg(blkg); |
| |
| if (iocg) { |
| spin_lock(&iocg->ioc->lock); |
| ioc_now(iocg->ioc, &now); |
| weight_updated(iocg, &now); |
| spin_unlock(&iocg->ioc->lock); |
| } |
| } |
| spin_unlock_irq(&blkcg->lock); |
| |
| return nbytes; |
| } |
| |
| blkg_conf_init(&ctx, buf); |
| |
| ret = blkg_conf_prep(blkcg, &blkcg_policy_iocost, &ctx); |
| if (ret) |
| goto err; |
| |
| iocg = blkg_to_iocg(ctx.blkg); |
| |
| if (!strncmp(ctx.body, "default", 7)) { |
| v = 0; |
| } else { |
| if (!sscanf(ctx.body, "%u", &v)) |
| goto einval; |
| if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX) |
| goto einval; |
| } |
| |
| spin_lock(&iocg->ioc->lock); |
| iocg->cfg_weight = v * WEIGHT_ONE; |
| ioc_now(iocg->ioc, &now); |
| weight_updated(iocg, &now); |
| spin_unlock(&iocg->ioc->lock); |
| |
| blkg_conf_exit(&ctx); |
| return nbytes; |
| |
| einval: |
| ret = -EINVAL; |
| err: |
| blkg_conf_exit(&ctx); |
| return ret; |
| } |
| |
| static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd, |
| int off) |
| { |
| const char *dname = blkg_dev_name(pd->blkg); |
|