blob: 9d5c94870129971fbc2011bc5972286e09323af5 [file] [log] [blame]
/*
* 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 INT_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 <trace/events/block.h>
#include "blk-wbt.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;
/* 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 iolatency_grp {
struct blkg_policy_data pd;
struct blk_rq_stat __percpu *stats;
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 total_lat_avg;
u64 total_lat_nr;
struct child_latency_info child_lat;
};
static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd)
{
return container_of(pd, struct iolatency_grp, pd);
}
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 bool iolatency_may_queue(struct iolatency_grp *iolat,
wait_queue_entry_t *wait)
{
struct rq_wait *rqw = &iolat->rq_wait;
if (waitqueue_active(&rqw->wait) &&
rqw->wait.head.next != &wait->entry)
return false;
return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth);
}
static void __blkcg_iolatency_throttle(struct rq_qos *rqos,
struct iolatency_grp *iolat,
spinlock_t *lock, bool issue_as_root,
bool use_memdelay)
__releases(lock)
__acquires(lock)
{
struct rq_wait *rqw = &iolat->rq_wait;
unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay);
DEFINE_WAIT(wait);
if (use_delay)
blkcg_schedule_throttle(rqos->q, use_memdelay);
/* We don't wait for a qd slot, we just take what we want. */
if (issue_as_root) {
atomic_inc(&rqw->inflight);
return;
}
if (iolatency_may_queue(iolat, &wait))
return;
do {
prepare_to_wait_exclusive(&rqw->wait, &wait,
TASK_UNINTERRUPTIBLE);
if (iolatency_may_queue(iolat, &wait))
break;
if (lock) {
spin_unlock_irq(lock);
io_schedule();
spin_lock_irq(lock);
} else {
io_schedule();
}
} while (1);
finish_wait(&rqw->wait, &wait);
}
#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.
*/
static void scale_cookie_change(struct blk_iolatency *blkiolat,
struct child_latency_info *lat_info,
bool up)
{
unsigned long qd = blk_queue_depth(blkiolat->rqos.q);
unsigned long scale = scale_amount(qd, up);
unsigned long old = atomic_read(&lat_info->scale_cookie);
if (up) {
if (scale + old > DEFAULT_SCALE_COOKIE)
atomic_set(&lat_info->scale_cookie,
DEFAULT_SCALE_COOKIE);
else if (DEFAULT_SCALE_COOKIE - old > qd)
atomic_inc(&lat_info->scale_cookie);
else
atomic_add(scale, &lat_info->scale_cookie);
} else {
if (DEFAULT_SCALE_COOKIE - old > qd)
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 = blk_queue_depth(iolat->blkiolat->rqos.q);
unsigned long scale = scale_amount(qd, up);
unsigned long old = iolat->rq_depth.max_depth;
bool changed = false;
if (old > qd)
old = qd;
if (up) {
if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat)))
return;
if (old < qd) {
changed = true;
old += scale;
old = min(old, qd);
iolat->rq_depth.max_depth = old;
wake_up_all(&iolat->rq_wait.wait);
}
} else if (old > 1) {
old >>= 1;
changed = true;
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);
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 && (!scale_lat || iolat->min_lat_nsec <= scale_lat))
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 = INT_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,
spinlock_t *lock)
{
struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
struct blkcg *blkcg;
struct blkcg_gq *blkg;
struct request_queue *q = rqos->q;
bool issue_as_root = bio_issue_as_root_blkg(bio);
if (!blk_iolatency_enabled(blkiolat))
return;
rcu_read_lock();
blkcg = bio_blkcg(bio);
bio_associate_blkcg(bio, &blkcg->css);
blkg = blkg_lookup(blkcg, q);
if (unlikely(!blkg)) {
if (!lock)
spin_lock_irq(q->queue_lock);
blkg = blkg_lookup_create(blkcg, q);
if (IS_ERR(blkg))
blkg = NULL;
if (!lock)
spin_unlock_irq(q->queue_lock);
}
if (!blkg)
goto out;
bio_issue_init(&bio->bi_issue, bio_sectors(bio));
bio_associate_blkg(bio, blkg);
out:
rcu_read_unlock();
while (blkg && blkg->parent) {
struct iolatency_grp *iolat = blkg_to_lat(blkg);
check_scale_change(iolat);
__blkcg_iolatency_throttle(rqos, iolat, lock, 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)
{
struct blk_rq_stat *rq_stat;
u64 start = bio_issue_time(issue);
u64 req_time;
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 != (u64)-1)) {
u64 sub = iolat->min_lat_nsec;
if (req_time < sub)
blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time);
return;
}
rq_stat = get_cpu_ptr(iolat->stats);
blk_rq_stat_add(rq_stat, req_time);
put_cpu_ptr(rq_stat);
}
#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 blk_rq_stat stat;
unsigned long flags;
int cpu;
blk_rq_stat_init(&stat);
preempt_disable();
for_each_online_cpu(cpu) {
struct blk_rq_stat *s;
s = per_cpu_ptr(iolat->stats, cpu);
blk_rq_stat_sum(&stat, s);
blk_rq_stat_init(s);
}
preempt_enable();
/*
* Our average exceeded our window, scale up our window so we are more
* accurate, but not more than the global timer.
*/
if (stat.mean > iolat->cur_win_nsec) {
iolat->cur_win_nsec <<= 1;
iolat->cur_win_nsec =
max_t(u64, iolat->cur_win_nsec, NSEC_PER_SEC);
}
if (!blkg->parent)
return;
parent = blkg_to_lat(blkg->parent);
lat_info = &parent->child_lat;
iolat->total_lat_avg =
div64_u64((iolat->total_lat_avg * iolat->total_lat_nr) +
stat.mean, iolat->total_lat_nr + 1);
iolat->total_lat_nr++;
/* Everything is ok and we don't need to adjust the scale. */
if (stat.mean <= iolat->min_lat_nsec &&
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);
if ((lat_info->last_scale_event >= now ||
now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME) &&
lat_info->scale_lat <= iolat->min_lat_nsec)
goto out;
if (stat.mean <= iolat->min_lat_nsec &&
stat.nr_samples >= BLKIOLATENCY_MIN_GOOD_SAMPLES) {
lat_info->last_scale_event = now;
if (lat_info->scale_grp == iolat)
scale_cookie_change(iolat->blkiolat, lat_info, true);
} else if (stat.mean > 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);
}
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;
blkg = bio->bi_blkg;
if (!blkg)
return;
iolat = blkg_to_lat(blkg);
enabled = blk_iolatency_enabled(iolat->blkiolat);
while (blkg->parent) {
iolat = blkg_to_lat(blkg);
rqw = &iolat->rq_wait;
atomic_dec(&rqw->inflight);
if (!enabled || iolat->min_lat_nsec == 0)
goto next;
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);
}
next:
wake_up_all(&rqw->wait);
blkg = blkg->parent;
}
}
static void blkcg_iolatency_cleanup(struct rq_qos *rqos, struct bio *bio)
{
struct blkcg_gq *blkg;
blkg = bio->bi_blkg;
while (blkg && blkg->parent) {
struct rq_wait *rqw;
struct iolatency_grp *iolat;
iolat = blkg_to_lat(blkg);
rqw = &iolat->rq_wait;
atomic_dec(&rqw->inflight);
wake_up_all(&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,
.cleanup = blkcg_iolatency_cleanup,
.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 = blkg_to_lat(blkg);
struct child_latency_info *lat_info = &iolat->child_lat;
unsigned long flags;
u64 cookie = atomic_read(&lat_info->scale_cookie);
if (cookie >= DEFAULT_SCALE_COOKIE)
continue;
spin_lock_irqsave(&lat_info->lock, flags);
if (lat_info->last_scale_event >= now)
goto next;
/*
* 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;
}
/*
* 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:
spin_unlock_irqrestore(&lat_info->lock, flags);
}
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_CGROUP;
rqos->ops = &blkcg_iolatency_ops;
rqos->q = q;
rq_qos_add(q, rqos);
ret = blkcg_activate_policy(q, &blkcg_policy_iolatency);
if (ret) {
kfree(blkiolat);
return ret;
}
timer_setup(&blkiolat->timer, blkiolatency_timer_fn,
(unsigned long)blkiolat);
return 0;
}
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, 100 * NSEC_PER_MSEC);
iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec, NSEC_PER_SEC);
if (!oldval && val)
atomic_inc(&blkiolat->enabled);
if (oldval && !val)
atomic_dec(&blkiolat->enabled);
}
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 = &iolat->child_lat;
spin_lock_irq(&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_irq(&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 blk_iolatency *blkiolat;
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);
blkiolat = iolat->blkiolat;
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,
(unsigned long long)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_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 = div64_u64(iolat->total_lat_avg, NSEC_PER_USEC);
if (!iolat->min_lat_nsec)
return 0;
if (iolat->rq_depth.max_depth == (u64)-1)
return scnprintf(buf, size, " depth=max avg_lat=%llu",
avg_lat);
return scnprintf(buf, size, " depth=%u avg_lat=%llu",
iolat->rq_depth.max_depth, avg_lat);
}
static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, int node)
{
struct iolatency_grp *iolat;
iolat = kzalloc_node(sizeof(*iolat), gfp, node);
if (!iolat)
return NULL;
iolat->stats = __alloc_percpu_gfp(sizeof(struct blk_rq_stat),
__alignof__(struct blk_rq_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;
for_each_possible_cpu(cpu) {
struct blk_rq_stat *stat;
stat = per_cpu_ptr(iolat->stats, cpu);
blk_rq_stat_init(stat);
}
rq_wait_init(&iolat->rq_wait);
spin_lock_init(&iolat->child_lat.lock);
iolat->rq_depth.queue_depth = blk_queue_depth(blkg->q);
iolat->rq_depth.max_depth = INT_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)
{
return blkcg_policy_unregister(&blkcg_policy_iolatency);
}
module_init(iolatency_init);
module_exit(iolatency_exit);