| // 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 = ktime_to_ns(ktime_get()); |
| 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; |
| |
| 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) |
| { |
| return blkcg_policy_unregister(&blkcg_policy_iolatency); |
| } |
| |
| module_init(iolatency_init); |
| module_exit(iolatency_exit); |