Author | Tokens | Token Proportion | Commits | Commit Proportion |
---|---|---|---|---|
Josef Bacik | 3179 | 73.47% | 2 | 5.56% |
Josef Whiter | 759 | 17.54% | 8 | 22.22% |
Tejun Heo | 183 | 4.23% | 6 | 16.67% |
Dennis Zhou | 86 | 1.99% | 6 | 16.67% |
Jinke Han | 31 | 0.72% | 1 | 2.78% |
Liu Bo | 26 | 0.60% | 2 | 5.56% |
Christoph Hellwig | 24 | 0.55% | 3 | 8.33% |
Uros Bizjak | 10 | 0.23% | 1 | 2.78% |
Hongnan Li | 8 | 0.18% | 1 | 2.78% |
Johannes Weiner | 7 | 0.16% | 1 | 2.78% |
Arnd Bergmann | 4 | 0.09% | 1 | 2.78% |
Wolfgang Bumiller | 3 | 0.07% | 1 | 2.78% |
Ming Lei | 3 | 0.07% | 1 | 2.78% |
Bart Van Assche | 3 | 0.07% | 1 | 2.78% |
Baolin Wang | 1 | 0.02% | 1 | 2.78% |
Total | 4327 | 36 |
// 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-cgroup.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; /* * ->enabled is the master enable switch gating the throttling logic and * inflight tracking. The number of cgroups which have iolat enabled is * tracked in ->enable_cnt, and ->enable is flipped on/off accordingly * from ->enable_work with the request_queue frozen. For details, See * blkiolatency_enable_work_fn(). */ bool enabled; atomic_t enable_cnt; struct work_struct enable_work; }; static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos) { return container_of(rqos, struct blk_iolatency, rqos); } 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; 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; if (!atomic_try_cmpxchg(&iolat->scale_cookie, &our_cookie, cur_cookie)) { /* Somebody beat us to the punch, just bail. */ 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 (!blkiolat->enabled) 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); int inflight = 0; blkg = bio->bi_blkg; if (!blkg || !bio_flagged(bio, BIO_QOS_THROTTLED)) return; iolat = blkg_to_lat(bio->bi_blkg); if (!iolat) return; if (!iolat->blkiolat->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_try_cmpxchg(&iolat->window_start, &window_start, now)) 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); flush_work(&blkiolat->enable_work); 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(); } /** * blkiolatency_enable_work_fn - Enable or disable iolatency on the device * @work: enable_work of the blk_iolatency of interest * * iolatency needs to keep track of the number of in-flight IOs per cgroup. This * is relatively expensive as it involves walking up the hierarchy twice for * every IO. Thus, if iolatency is not enabled in any cgroup for the device, we * want to disable the in-flight tracking. * * We have to make sure that the counting is balanced - we don't want to leak * the in-flight counts by disabling accounting in the completion path while IOs * are in flight. This is achieved by ensuring that no IO is in flight by * freezing the queue while flipping ->enabled. As this requires a sleepable * context, ->enabled flipping is punted to this work function. */ static void blkiolatency_enable_work_fn(struct work_struct *work) { struct blk_iolatency *blkiolat = container_of(work, struct blk_iolatency, enable_work); bool enabled; /* * There can only be one instance of this function running for @blkiolat * and it's guaranteed to be executed at least once after the latest * ->enabled_cnt modification. Acting on the latest ->enable_cnt is * sufficient. * * Also, we know @blkiolat is safe to access as ->enable_work is flushed * in blkcg_iolatency_exit(). */ enabled = atomic_read(&blkiolat->enable_cnt); if (enabled != blkiolat->enabled) { blk_mq_freeze_queue(blkiolat->rqos.q); blkiolat->enabled = enabled; blk_mq_unfreeze_queue(blkiolat->rqos.q); } } 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; ret = rq_qos_add(q, rqos); if (ret) goto err_free; ret = blkcg_activate_policy(q, &blkcg_policy_iolatency); if (ret) goto err_qos_del; timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0); INIT_WORK(&blkiolat->enable_work, blkiolatency_enable_work_fn); return 0; err_qos_del: rq_qos_del(q, rqos); err_free: kfree(blkiolat); return ret; } static void iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val) { struct iolatency_grp *iolat = blkg_to_lat(blkg); struct blk_iolatency *blkiolat = iolat->blkiolat; 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) { if (atomic_inc_return(&blkiolat->enable_cnt) == 1) schedule_work(&blkiolat->enable_work); } if (oldval && !val) { blkcg_clear_delay(blkg); if (atomic_dec_return(&blkiolat->enable_cnt) == 0) schedule_work(&blkiolat->enable_work); } } 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; 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; iolatency_set_min_lat_nsec(blkg, lat_val); if (oldval != iolat->min_lat_nsec) iolatency_clear_scaling(blkg); ret = 0; out: blkg_conf_finish(&ctx); 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 void iolatency_ssd_stat(struct iolatency_grp *iolat, struct seq_file *s) { 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) seq_printf(s, " missed=%llu total=%llu depth=max", (unsigned long long)stat.ps.missed, (unsigned long long)stat.ps.total); else seq_printf(s, " missed=%llu total=%llu depth=%u", (unsigned long long)stat.ps.missed, (unsigned long long)stat.ps.total, iolat->rq_depth.max_depth); } static void iolatency_pd_stat(struct blkg_policy_data *pd, struct seq_file *s) { struct iolatency_grp *iolat = pd_to_lat(pd); unsigned long long avg_lat; unsigned long long cur_win; if (!blkcg_debug_stats) return; if (iolat->ssd) return iolatency_ssd_stat(iolat, s); 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) seq_printf(s, " depth=max avg_lat=%llu win=%llu", avg_lat, cur_win); else seq_printf(s, " 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); iolatency_set_min_lat_nsec(blkg, 0); 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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