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- // SPDX-License-Identifier: GPL-2.0
- /*
- * Block rq-qos base io controller
- *
- * This works similar to wbt with a few exceptions
- *
- * - It's bio based, so the latency covers the whole block layer in addition to
- * the actual io.
- * - We will throttle all IO that comes in here if we need to.
- * - We use the mean latency over the 100ms window. This is because writes can
- * be particularly fast, which could give us a false sense of the impact of
- * other workloads on our protected workload.
- * - By default there's no throttling, we set the queue_depth to UINT_MAX so
- * that we can have as many outstanding bio's as we're allowed to. Only at
- * throttle time do we pay attention to the actual queue depth.
- *
- * The hierarchy works like the cpu controller does, we track the latency at
- * every configured node, and each configured node has it's own independent
- * queue depth. This means that we only care about our latency targets at the
- * peer level. Some group at the bottom of the hierarchy isn't going to affect
- * a group at the end of some other path if we're only configred at leaf level.
- *
- * Consider the following
- *
- * root blkg
- * / \
- * fast (target=5ms) slow (target=10ms)
- * / \ / \
- * a b normal(15ms) unloved
- *
- * "a" and "b" have no target, but their combined io under "fast" cannot exceed
- * an average latency of 5ms. If it does then we will throttle the "slow"
- * group. In the case of "normal", if it exceeds its 15ms target, we will
- * throttle "unloved", but nobody else.
- *
- * In this example "fast", "slow", and "normal" will be the only groups actually
- * accounting their io latencies. We have to walk up the heirarchy to the root
- * on every submit and complete so we can do the appropriate stat recording and
- * adjust the queue depth of ourselves if needed.
- *
- * There are 2 ways we throttle IO.
- *
- * 1) Queue depth throttling. As we throttle down we will adjust the maximum
- * number of IO's we're allowed to have in flight. This starts at (u64)-1 down
- * to 1. If the group is only ever submitting IO for itself then this is the
- * only way we throttle.
- *
- * 2) Induced delay throttling. This is for the case that a group is generating
- * IO that has to be issued by the root cg to avoid priority inversion. So think
- * REQ_META or REQ_SWAP. If we are already at qd == 1 and we're getting a lot
- * of work done for us on behalf of the root cg and are being asked to scale
- * down more then we induce a latency at userspace return. We accumulate the
- * total amount of time we need to be punished by doing
- *
- * total_time += min_lat_nsec - actual_io_completion
- *
- * and then at throttle time will do
- *
- * throttle_time = min(total_time, NSEC_PER_SEC)
- *
- * This induced delay will throttle back the activity that is generating the
- * root cg issued io's, wethere that's some metadata intensive operation or the
- * group is using so much memory that it is pushing us into swap.
- *
- * Copyright (C) 2018 Josef Bacik
- */
- #include <linux/kernel.h>
- #include <linux/blk_types.h>
- #include <linux/backing-dev.h>
- #include <linux/module.h>
- #include <linux/timer.h>
- #include <linux/memcontrol.h>
- #include <linux/sched/loadavg.h>
- #include <linux/sched/signal.h>
- #include <trace/events/block.h>
- #include <linux/blk-mq.h>
- #include "blk-rq-qos.h"
- #include "blk-stat.h"
- #include "blk.h"
- #define DEFAULT_SCALE_COOKIE 1000000U
- static struct blkcg_policy blkcg_policy_iolatency;
- struct iolatency_grp;
- struct blk_iolatency {
- struct rq_qos rqos;
- struct timer_list timer;
- atomic_t enabled;
- };
- static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos)
- {
- return container_of(rqos, struct blk_iolatency, rqos);
- }
- static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat)
- {
- return atomic_read(&blkiolat->enabled) > 0;
- }
- struct child_latency_info {
- spinlock_t lock;
- /* Last time we adjusted the scale of everybody. */
- u64 last_scale_event;
- /* The latency that we missed. */
- u64 scale_lat;
- /* Total io's from all of our children for the last summation. */
- u64 nr_samples;
- /* The guy who actually changed the latency numbers. */
- struct iolatency_grp *scale_grp;
- /* Cookie to tell if we need to scale up or down. */
- atomic_t scale_cookie;
- };
- struct percentile_stats {
- u64 total;
- u64 missed;
- };
- struct latency_stat {
- union {
- struct percentile_stats ps;
- struct blk_rq_stat rqs;
- };
- };
- struct iolatency_grp {
- struct blkg_policy_data pd;
- struct latency_stat __percpu *stats;
- struct latency_stat cur_stat;
- struct blk_iolatency *blkiolat;
- struct rq_depth rq_depth;
- struct rq_wait rq_wait;
- atomic64_t window_start;
- atomic_t scale_cookie;
- u64 min_lat_nsec;
- u64 cur_win_nsec;
- /* total running average of our io latency. */
- u64 lat_avg;
- /* Our current number of IO's for the last summation. */
- u64 nr_samples;
- bool ssd;
- struct child_latency_info child_lat;
- };
- #define BLKIOLATENCY_MIN_WIN_SIZE (100 * NSEC_PER_MSEC)
- #define BLKIOLATENCY_MAX_WIN_SIZE NSEC_PER_SEC
- /*
- * These are the constants used to fake the fixed-point moving average
- * calculation just like load average. The call to calc_load() folds
- * (FIXED_1 (2048) - exp_factor) * new_sample into lat_avg. The sampling
- * window size is bucketed to try to approximately calculate average
- * latency such that 1/exp (decay rate) is [1 min, 2.5 min) when windows
- * elapse immediately. Note, windows only elapse with IO activity. Idle
- * periods extend the most recent window.
- */
- #define BLKIOLATENCY_NR_EXP_FACTORS 5
- #define BLKIOLATENCY_EXP_BUCKET_SIZE (BLKIOLATENCY_MAX_WIN_SIZE / \
- (BLKIOLATENCY_NR_EXP_FACTORS - 1))
- static const u64 iolatency_exp_factors[BLKIOLATENCY_NR_EXP_FACTORS] = {
- 2045, // exp(1/600) - 600 samples
- 2039, // exp(1/240) - 240 samples
- 2031, // exp(1/120) - 120 samples
- 2023, // exp(1/80) - 80 samples
- 2014, // exp(1/60) - 60 samples
- };
- static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd)
- {
- return pd ? container_of(pd, struct iolatency_grp, pd) : NULL;
- }
- static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg)
- {
- return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency));
- }
- static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat)
- {
- return pd_to_blkg(&iolat->pd);
- }
- static inline void latency_stat_init(struct iolatency_grp *iolat,
- struct latency_stat *stat)
- {
- if (iolat->ssd) {
- stat->ps.total = 0;
- stat->ps.missed = 0;
- } else
- blk_rq_stat_init(&stat->rqs);
- }
- static inline void latency_stat_sum(struct iolatency_grp *iolat,
- struct latency_stat *sum,
- struct latency_stat *stat)
- {
- if (iolat->ssd) {
- sum->ps.total += stat->ps.total;
- sum->ps.missed += stat->ps.missed;
- } else
- blk_rq_stat_sum(&sum->rqs, &stat->rqs);
- }
- static inline void latency_stat_record_time(struct iolatency_grp *iolat,
- u64 req_time)
- {
- struct latency_stat *stat = get_cpu_ptr(iolat->stats);
- if (iolat->ssd) {
- if (req_time >= iolat->min_lat_nsec)
- stat->ps.missed++;
- stat->ps.total++;
- } else
- blk_rq_stat_add(&stat->rqs, req_time);
- put_cpu_ptr(stat);
- }
- static inline bool latency_sum_ok(struct iolatency_grp *iolat,
- struct latency_stat *stat)
- {
- if (iolat->ssd) {
- u64 thresh = div64_u64(stat->ps.total, 10);
- thresh = max(thresh, 1ULL);
- return stat->ps.missed < thresh;
- }
- return stat->rqs.mean <= iolat->min_lat_nsec;
- }
- static inline u64 latency_stat_samples(struct iolatency_grp *iolat,
- struct latency_stat *stat)
- {
- if (iolat->ssd)
- return stat->ps.total;
- return stat->rqs.nr_samples;
- }
- static inline void iolat_update_total_lat_avg(struct iolatency_grp *iolat,
- struct latency_stat *stat)
- {
- int exp_idx;
- if (iolat->ssd)
- return;
- /*
- * calc_load() takes in a number stored in fixed point representation.
- * Because we are using this for IO time in ns, the values stored
- * are significantly larger than the FIXED_1 denominator (2048).
- * Therefore, rounding errors in the calculation are negligible and
- * can be ignored.
- */
- exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1,
- div64_u64(iolat->cur_win_nsec,
- BLKIOLATENCY_EXP_BUCKET_SIZE));
- iolat->lat_avg = calc_load(iolat->lat_avg,
- iolatency_exp_factors[exp_idx],
- stat->rqs.mean);
- }
- static void iolat_cleanup_cb(struct rq_wait *rqw, void *private_data)
- {
- atomic_dec(&rqw->inflight);
- wake_up(&rqw->wait);
- }
- static bool iolat_acquire_inflight(struct rq_wait *rqw, void *private_data)
- {
- struct iolatency_grp *iolat = private_data;
- return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth);
- }
- static void __blkcg_iolatency_throttle(struct rq_qos *rqos,
- struct iolatency_grp *iolat,
- bool issue_as_root,
- bool use_memdelay)
- {
- struct rq_wait *rqw = &iolat->rq_wait;
- unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay);
- if (use_delay)
- blkcg_schedule_throttle(rqos->q, use_memdelay);
- /*
- * To avoid priority inversions we want to just take a slot if we are
- * issuing as root. If we're being killed off there's no point in
- * delaying things, we may have been killed by OOM so throttling may
- * make recovery take even longer, so just let the IO's through so the
- * task can go away.
- */
- if (issue_as_root || fatal_signal_pending(current)) {
- atomic_inc(&rqw->inflight);
- return;
- }
- rq_qos_wait(rqw, iolat, iolat_acquire_inflight, iolat_cleanup_cb);
- }
- #define SCALE_DOWN_FACTOR 2
- #define SCALE_UP_FACTOR 4
- static inline unsigned long scale_amount(unsigned long qd, bool up)
- {
- return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL);
- }
- /*
- * We scale the qd down faster than we scale up, so we need to use this helper
- * to adjust the scale_cookie accordingly so we don't prematurely get
- * scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much.
- *
- * Each group has their own local copy of the last scale cookie they saw, so if
- * the global scale cookie goes up or down they know which way they need to go
- * based on their last knowledge of it.
- */
- static void scale_cookie_change(struct blk_iolatency *blkiolat,
- struct child_latency_info *lat_info,
- bool up)
- {
- unsigned long qd = blkiolat->rqos.q->nr_requests;
- unsigned long scale = scale_amount(qd, up);
- unsigned long old = atomic_read(&lat_info->scale_cookie);
- unsigned long max_scale = qd << 1;
- unsigned long diff = 0;
- if (old < DEFAULT_SCALE_COOKIE)
- diff = DEFAULT_SCALE_COOKIE - old;
- if (up) {
- if (scale + old > DEFAULT_SCALE_COOKIE)
- atomic_set(&lat_info->scale_cookie,
- DEFAULT_SCALE_COOKIE);
- else if (diff > qd)
- atomic_inc(&lat_info->scale_cookie);
- else
- atomic_add(scale, &lat_info->scale_cookie);
- } else {
- /*
- * We don't want to dig a hole so deep that it takes us hours to
- * dig out of it. Just enough that we don't throttle/unthrottle
- * with jagged workloads but can still unthrottle once pressure
- * has sufficiently dissipated.
- */
- if (diff > qd) {
- if (diff < max_scale)
- atomic_dec(&lat_info->scale_cookie);
- } else {
- atomic_sub(scale, &lat_info->scale_cookie);
- }
- }
- }
- /*
- * Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the
- * queue depth at a time so we don't get wild swings and hopefully dial in to
- * fairer distribution of the overall queue depth.
- */
- static void scale_change(struct iolatency_grp *iolat, bool up)
- {
- unsigned long qd = iolat->blkiolat->rqos.q->nr_requests;
- unsigned long scale = scale_amount(qd, up);
- unsigned long old = iolat->rq_depth.max_depth;
- if (old > qd)
- old = qd;
- if (up) {
- if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat)))
- return;
- if (old < qd) {
- old += scale;
- old = min(old, qd);
- iolat->rq_depth.max_depth = old;
- wake_up_all(&iolat->rq_wait.wait);
- }
- } else {
- old >>= 1;
- iolat->rq_depth.max_depth = max(old, 1UL);
- }
- }
- /* Check our parent and see if the scale cookie has changed. */
- static void check_scale_change(struct iolatency_grp *iolat)
- {
- struct iolatency_grp *parent;
- struct child_latency_info *lat_info;
- unsigned int cur_cookie;
- unsigned int our_cookie = atomic_read(&iolat->scale_cookie);
- u64 scale_lat;
- unsigned int old;
- int direction = 0;
- if (lat_to_blkg(iolat)->parent == NULL)
- return;
- parent = blkg_to_lat(lat_to_blkg(iolat)->parent);
- if (!parent)
- return;
- lat_info = &parent->child_lat;
- cur_cookie = atomic_read(&lat_info->scale_cookie);
- scale_lat = READ_ONCE(lat_info->scale_lat);
- if (cur_cookie < our_cookie)
- direction = -1;
- else if (cur_cookie > our_cookie)
- direction = 1;
- else
- return;
- old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie);
- /* Somebody beat us to the punch, just bail. */
- if (old != our_cookie)
- return;
- if (direction < 0 && iolat->min_lat_nsec) {
- u64 samples_thresh;
- if (!scale_lat || iolat->min_lat_nsec <= scale_lat)
- return;
- /*
- * Sometimes high priority groups are their own worst enemy, so
- * instead of taking it out on some poor other group that did 5%
- * or less of the IO's for the last summation just skip this
- * scale down event.
- */
- samples_thresh = lat_info->nr_samples * 5;
- samples_thresh = max(1ULL, div64_u64(samples_thresh, 100));
- if (iolat->nr_samples <= samples_thresh)
- return;
- }
- /* We're as low as we can go. */
- if (iolat->rq_depth.max_depth == 1 && direction < 0) {
- blkcg_use_delay(lat_to_blkg(iolat));
- return;
- }
- /* We're back to the default cookie, unthrottle all the things. */
- if (cur_cookie == DEFAULT_SCALE_COOKIE) {
- blkcg_clear_delay(lat_to_blkg(iolat));
- iolat->rq_depth.max_depth = UINT_MAX;
- wake_up_all(&iolat->rq_wait.wait);
- return;
- }
- scale_change(iolat, direction > 0);
- }
- static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)
- {
- struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
- struct blkcg_gq *blkg = bio->bi_blkg;
- bool issue_as_root = bio_issue_as_root_blkg(bio);
- if (!blk_iolatency_enabled(blkiolat))
- return;
- while (blkg && blkg->parent) {
- struct iolatency_grp *iolat = blkg_to_lat(blkg);
- if (!iolat) {
- blkg = blkg->parent;
- continue;
- }
- check_scale_change(iolat);
- __blkcg_iolatency_throttle(rqos, iolat, issue_as_root,
- (bio->bi_opf & REQ_SWAP) == REQ_SWAP);
- blkg = blkg->parent;
- }
- if (!timer_pending(&blkiolat->timer))
- mod_timer(&blkiolat->timer, jiffies + HZ);
- }
- static void iolatency_record_time(struct iolatency_grp *iolat,
- struct bio_issue *issue, u64 now,
- bool issue_as_root)
- {
- u64 start = bio_issue_time(issue);
- u64 req_time;
- /*
- * Have to do this so we are truncated to the correct time that our
- * issue is truncated to.
- */
- now = __bio_issue_time(now);
- if (now <= start)
- return;
- req_time = now - start;
- /*
- * We don't want to count issue_as_root bio's in the cgroups latency
- * statistics as it could skew the numbers downwards.
- */
- if (unlikely(issue_as_root && iolat->rq_depth.max_depth != UINT_MAX)) {
- u64 sub = iolat->min_lat_nsec;
- if (req_time < sub)
- blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time);
- return;
- }
- latency_stat_record_time(iolat, req_time);
- }
- #define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC)
- #define BLKIOLATENCY_MIN_GOOD_SAMPLES 5
- static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now)
- {
- struct blkcg_gq *blkg = lat_to_blkg(iolat);
- struct iolatency_grp *parent;
- struct child_latency_info *lat_info;
- struct latency_stat stat;
- unsigned long flags;
- int cpu;
- latency_stat_init(iolat, &stat);
- preempt_disable();
- for_each_online_cpu(cpu) {
- struct latency_stat *s;
- s = per_cpu_ptr(iolat->stats, cpu);
- latency_stat_sum(iolat, &stat, s);
- latency_stat_init(iolat, s);
- }
- preempt_enable();
- parent = blkg_to_lat(blkg->parent);
- if (!parent)
- return;
- lat_info = &parent->child_lat;
- iolat_update_total_lat_avg(iolat, &stat);
- /* Everything is ok and we don't need to adjust the scale. */
- if (latency_sum_ok(iolat, &stat) &&
- atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE)
- return;
- /* Somebody beat us to the punch, just bail. */
- spin_lock_irqsave(&lat_info->lock, flags);
- latency_stat_sum(iolat, &iolat->cur_stat, &stat);
- lat_info->nr_samples -= iolat->nr_samples;
- lat_info->nr_samples += latency_stat_samples(iolat, &iolat->cur_stat);
- iolat->nr_samples = latency_stat_samples(iolat, &iolat->cur_stat);
- if ((lat_info->last_scale_event >= now ||
- now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME))
- goto out;
- if (latency_sum_ok(iolat, &iolat->cur_stat) &&
- latency_sum_ok(iolat, &stat)) {
- if (latency_stat_samples(iolat, &iolat->cur_stat) <
- BLKIOLATENCY_MIN_GOOD_SAMPLES)
- goto out;
- if (lat_info->scale_grp == iolat) {
- lat_info->last_scale_event = now;
- scale_cookie_change(iolat->blkiolat, lat_info, true);
- }
- } else if (lat_info->scale_lat == 0 ||
- lat_info->scale_lat >= iolat->min_lat_nsec) {
- lat_info->last_scale_event = now;
- if (!lat_info->scale_grp ||
- lat_info->scale_lat > iolat->min_lat_nsec) {
- WRITE_ONCE(lat_info->scale_lat, iolat->min_lat_nsec);
- lat_info->scale_grp = iolat;
- }
- scale_cookie_change(iolat->blkiolat, lat_info, false);
- }
- latency_stat_init(iolat, &iolat->cur_stat);
- out:
- spin_unlock_irqrestore(&lat_info->lock, flags);
- }
- static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio)
- {
- struct blkcg_gq *blkg;
- struct rq_wait *rqw;
- struct iolatency_grp *iolat;
- u64 window_start;
- u64 now;
- bool issue_as_root = bio_issue_as_root_blkg(bio);
- bool enabled = false;
- int inflight = 0;
- blkg = bio->bi_blkg;
- if (!blkg || !bio_flagged(bio, BIO_TRACKED))
- return;
- iolat = blkg_to_lat(bio->bi_blkg);
- if (!iolat)
- return;
- enabled = blk_iolatency_enabled(iolat->blkiolat);
- if (!enabled)
- return;
- now = ktime_to_ns(ktime_get());
- while (blkg && blkg->parent) {
- iolat = blkg_to_lat(blkg);
- if (!iolat) {
- blkg = blkg->parent;
- continue;
- }
- rqw = &iolat->rq_wait;
- inflight = atomic_dec_return(&rqw->inflight);
- WARN_ON_ONCE(inflight < 0);
- /*
- * If bi_status is BLK_STS_AGAIN, the bio wasn't actually
- * submitted, so do not account for it.
- */
- if (iolat->min_lat_nsec && bio->bi_status != BLK_STS_AGAIN) {
- iolatency_record_time(iolat, &bio->bi_issue, now,
- issue_as_root);
- window_start = atomic64_read(&iolat->window_start);
- if (now > window_start &&
- (now - window_start) >= iolat->cur_win_nsec) {
- if (atomic64_cmpxchg(&iolat->window_start,
- window_start, now) == window_start)
- iolatency_check_latencies(iolat, now);
- }
- }
- wake_up(&rqw->wait);
- blkg = blkg->parent;
- }
- }
- static void blkcg_iolatency_exit(struct rq_qos *rqos)
- {
- struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
- del_timer_sync(&blkiolat->timer);
- blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency);
- kfree(blkiolat);
- }
- static struct rq_qos_ops blkcg_iolatency_ops = {
- .throttle = blkcg_iolatency_throttle,
- .done_bio = blkcg_iolatency_done_bio,
- .exit = blkcg_iolatency_exit,
- };
- static void blkiolatency_timer_fn(struct timer_list *t)
- {
- struct blk_iolatency *blkiolat = from_timer(blkiolat, t, timer);
- struct blkcg_gq *blkg;
- struct cgroup_subsys_state *pos_css;
- u64 now = ktime_to_ns(ktime_get());
- rcu_read_lock();
- blkg_for_each_descendant_pre(blkg, pos_css,
- blkiolat->rqos.q->root_blkg) {
- struct iolatency_grp *iolat;
- struct child_latency_info *lat_info;
- unsigned long flags;
- u64 cookie;
- /*
- * We could be exiting, don't access the pd unless we have a
- * ref on the blkg.
- */
- if (!blkg_tryget(blkg))
- continue;
- iolat = blkg_to_lat(blkg);
- if (!iolat)
- goto next;
- lat_info = &iolat->child_lat;
- cookie = atomic_read(&lat_info->scale_cookie);
- if (cookie >= DEFAULT_SCALE_COOKIE)
- goto next;
- spin_lock_irqsave(&lat_info->lock, flags);
- if (lat_info->last_scale_event >= now)
- goto next_lock;
- /*
- * We scaled down but don't have a scale_grp, scale up and carry
- * on.
- */
- if (lat_info->scale_grp == NULL) {
- scale_cookie_change(iolat->blkiolat, lat_info, true);
- goto next_lock;
- }
- /*
- * It's been 5 seconds since our last scale event, clear the
- * scale grp in case the group that needed the scale down isn't
- * doing any IO currently.
- */
- if (now - lat_info->last_scale_event >=
- ((u64)NSEC_PER_SEC * 5))
- lat_info->scale_grp = NULL;
- next_lock:
- spin_unlock_irqrestore(&lat_info->lock, flags);
- next:
- blkg_put(blkg);
- }
- rcu_read_unlock();
- }
- int blk_iolatency_init(struct request_queue *q)
- {
- struct blk_iolatency *blkiolat;
- struct rq_qos *rqos;
- int ret;
- blkiolat = kzalloc(sizeof(*blkiolat), GFP_KERNEL);
- if (!blkiolat)
- return -ENOMEM;
- rqos = &blkiolat->rqos;
- rqos->id = RQ_QOS_LATENCY;
- rqos->ops = &blkcg_iolatency_ops;
- rqos->q = q;
- rq_qos_add(q, rqos);
- ret = blkcg_activate_policy(q, &blkcg_policy_iolatency);
- if (ret) {
- rq_qos_del(q, rqos);
- kfree(blkiolat);
- return ret;
- }
- timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0);
- return 0;
- }
- /*
- * return 1 for enabling iolatency, return -1 for disabling iolatency, otherwise
- * return 0.
- */
- static int iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val)
- {
- struct iolatency_grp *iolat = blkg_to_lat(blkg);
- u64 oldval = iolat->min_lat_nsec;
- iolat->min_lat_nsec = val;
- iolat->cur_win_nsec = max_t(u64, val << 4, BLKIOLATENCY_MIN_WIN_SIZE);
- iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec,
- BLKIOLATENCY_MAX_WIN_SIZE);
- if (!oldval && val)
- return 1;
- if (oldval && !val) {
- blkcg_clear_delay(blkg);
- return -1;
- }
- return 0;
- }
- static void iolatency_clear_scaling(struct blkcg_gq *blkg)
- {
- if (blkg->parent) {
- struct iolatency_grp *iolat = blkg_to_lat(blkg->parent);
- struct child_latency_info *lat_info;
- if (!iolat)
- return;
- lat_info = &iolat->child_lat;
- spin_lock(&lat_info->lock);
- atomic_set(&lat_info->scale_cookie, DEFAULT_SCALE_COOKIE);
- lat_info->last_scale_event = 0;
- lat_info->scale_grp = NULL;
- lat_info->scale_lat = 0;
- spin_unlock(&lat_info->lock);
- }
- }
- static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf,
- size_t nbytes, loff_t off)
- {
- struct blkcg *blkcg = css_to_blkcg(of_css(of));
- struct blkcg_gq *blkg;
- struct blkg_conf_ctx ctx;
- struct iolatency_grp *iolat;
- char *p, *tok;
- u64 lat_val = 0;
- u64 oldval;
- int ret;
- int enable = 0;
- ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx);
- if (ret)
- return ret;
- iolat = blkg_to_lat(ctx.blkg);
- p = ctx.body;
- ret = -EINVAL;
- while ((tok = strsep(&p, " "))) {
- char key[16];
- char val[21]; /* 18446744073709551616 */
- if (sscanf(tok, "%15[^=]=%20s", key, val) != 2)
- goto out;
- if (!strcmp(key, "target")) {
- u64 v;
- if (!strcmp(val, "max"))
- lat_val = 0;
- else if (sscanf(val, "%llu", &v) == 1)
- lat_val = v * NSEC_PER_USEC;
- else
- goto out;
- } else {
- goto out;
- }
- }
- /* Walk up the tree to see if our new val is lower than it should be. */
- blkg = ctx.blkg;
- oldval = iolat->min_lat_nsec;
- enable = iolatency_set_min_lat_nsec(blkg, lat_val);
- if (enable) {
- if (!blk_get_queue(blkg->q)) {
- ret = -ENODEV;
- goto out;
- }
- blkg_get(blkg);
- }
- if (oldval != iolat->min_lat_nsec) {
- iolatency_clear_scaling(blkg);
- }
- ret = 0;
- out:
- blkg_conf_finish(&ctx);
- if (ret == 0 && enable) {
- struct iolatency_grp *tmp = blkg_to_lat(blkg);
- struct blk_iolatency *blkiolat = tmp->blkiolat;
- blk_mq_freeze_queue(blkg->q);
- if (enable == 1)
- atomic_inc(&blkiolat->enabled);
- else if (enable == -1)
- atomic_dec(&blkiolat->enabled);
- else
- WARN_ON_ONCE(1);
- blk_mq_unfreeze_queue(blkg->q);
- blkg_put(blkg);
- blk_put_queue(blkg->q);
- }
- return ret ?: nbytes;
- }
- static u64 iolatency_prfill_limit(struct seq_file *sf,
- struct blkg_policy_data *pd, int off)
- {
- struct iolatency_grp *iolat = pd_to_lat(pd);
- const char *dname = blkg_dev_name(pd->blkg);
- if (!dname || !iolat->min_lat_nsec)
- return 0;
- seq_printf(sf, "%s target=%llu\n",
- dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC));
- return 0;
- }
- static int iolatency_print_limit(struct seq_file *sf, void *v)
- {
- blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
- iolatency_prfill_limit,
- &blkcg_policy_iolatency, seq_cft(sf)->private, false);
- return 0;
- }
- static size_t iolatency_ssd_stat(struct iolatency_grp *iolat, char *buf,
- size_t size)
- {
- struct latency_stat stat;
- int cpu;
- latency_stat_init(iolat, &stat);
- preempt_disable();
- for_each_online_cpu(cpu) {
- struct latency_stat *s;
- s = per_cpu_ptr(iolat->stats, cpu);
- latency_stat_sum(iolat, &stat, s);
- }
- preempt_enable();
- if (iolat->rq_depth.max_depth == UINT_MAX)
- return scnprintf(buf, size, " missed=%llu total=%llu depth=max",
- (unsigned long long)stat.ps.missed,
- (unsigned long long)stat.ps.total);
- return scnprintf(buf, size, " missed=%llu total=%llu depth=%u",
- (unsigned long long)stat.ps.missed,
- (unsigned long long)stat.ps.total,
- iolat->rq_depth.max_depth);
- }
- static size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf,
- size_t size)
- {
- struct iolatency_grp *iolat = pd_to_lat(pd);
- unsigned long long avg_lat;
- unsigned long long cur_win;
- if (!blkcg_debug_stats)
- return 0;
- if (iolat->ssd)
- return iolatency_ssd_stat(iolat, buf, size);
- avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC);
- cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC);
- if (iolat->rq_depth.max_depth == UINT_MAX)
- return scnprintf(buf, size, " depth=max avg_lat=%llu win=%llu",
- avg_lat, cur_win);
- return scnprintf(buf, size, " depth=%u avg_lat=%llu win=%llu",
- iolat->rq_depth.max_depth, avg_lat, cur_win);
- }
- static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp,
- struct request_queue *q,
- struct blkcg *blkcg)
- {
- struct iolatency_grp *iolat;
- iolat = kzalloc_node(sizeof(*iolat), gfp, q->node);
- if (!iolat)
- return NULL;
- iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat),
- __alignof__(struct latency_stat), gfp);
- if (!iolat->stats) {
- kfree(iolat);
- return NULL;
- }
- return &iolat->pd;
- }
- static void iolatency_pd_init(struct blkg_policy_data *pd)
- {
- struct iolatency_grp *iolat = pd_to_lat(pd);
- struct blkcg_gq *blkg = lat_to_blkg(iolat);
- struct rq_qos *rqos = blkcg_rq_qos(blkg->q);
- struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
- u64 now = ktime_to_ns(ktime_get());
- int cpu;
- if (blk_queue_nonrot(blkg->q))
- iolat->ssd = true;
- else
- iolat->ssd = false;
- for_each_possible_cpu(cpu) {
- struct latency_stat *stat;
- stat = per_cpu_ptr(iolat->stats, cpu);
- latency_stat_init(iolat, stat);
- }
- latency_stat_init(iolat, &iolat->cur_stat);
- rq_wait_init(&iolat->rq_wait);
- spin_lock_init(&iolat->child_lat.lock);
- iolat->rq_depth.queue_depth = blkg->q->nr_requests;
- iolat->rq_depth.max_depth = UINT_MAX;
- iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth;
- iolat->blkiolat = blkiolat;
- iolat->cur_win_nsec = 100 * NSEC_PER_MSEC;
- atomic64_set(&iolat->window_start, now);
- /*
- * We init things in list order, so the pd for the parent may not be
- * init'ed yet for whatever reason.
- */
- if (blkg->parent && blkg_to_pd(blkg->parent, &blkcg_policy_iolatency)) {
- struct iolatency_grp *parent = blkg_to_lat(blkg->parent);
- atomic_set(&iolat->scale_cookie,
- atomic_read(&parent->child_lat.scale_cookie));
- } else {
- atomic_set(&iolat->scale_cookie, DEFAULT_SCALE_COOKIE);
- }
- atomic_set(&iolat->child_lat.scale_cookie, DEFAULT_SCALE_COOKIE);
- }
- static void iolatency_pd_offline(struct blkg_policy_data *pd)
- {
- struct iolatency_grp *iolat = pd_to_lat(pd);
- struct blkcg_gq *blkg = lat_to_blkg(iolat);
- struct blk_iolatency *blkiolat = iolat->blkiolat;
- int ret;
- ret = iolatency_set_min_lat_nsec(blkg, 0);
- if (ret == 1)
- atomic_inc(&blkiolat->enabled);
- if (ret == -1)
- atomic_dec(&blkiolat->enabled);
- iolatency_clear_scaling(blkg);
- }
- static void iolatency_pd_free(struct blkg_policy_data *pd)
- {
- struct iolatency_grp *iolat = pd_to_lat(pd);
- free_percpu(iolat->stats);
- kfree(iolat);
- }
- static struct cftype iolatency_files[] = {
- {
- .name = "latency",
- .flags = CFTYPE_NOT_ON_ROOT,
- .seq_show = iolatency_print_limit,
- .write = iolatency_set_limit,
- },
- {}
- };
- static struct blkcg_policy blkcg_policy_iolatency = {
- .dfl_cftypes = iolatency_files,
- .pd_alloc_fn = iolatency_pd_alloc,
- .pd_init_fn = iolatency_pd_init,
- .pd_offline_fn = iolatency_pd_offline,
- .pd_free_fn = iolatency_pd_free,
- .pd_stat_fn = iolatency_pd_stat,
- };
- static int __init iolatency_init(void)
- {
- return blkcg_policy_register(&blkcg_policy_iolatency);
- }
- static void __exit iolatency_exit(void)
- {
- blkcg_policy_unregister(&blkcg_policy_iolatency);
- }
- module_init(iolatency_init);
- module_exit(iolatency_exit);
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