blk-wbt: add general throttling mechanism

We can hook this up to the block layer, to help throttle buffered
writes.

wbt registers a few trace points that can be used to track what is
happening in the system:

wbt_lat: 259:0: latency 2446318
wbt_stat: 259:0: rmean=2446318, rmin=2446318, rmax=2446318, rsamples=1,
               wmean=518866, wmin=15522, wmax=5330353, wsamples=57
wbt_step: 259:0: step down: step=1, window=72727272, background=8, normal=16, max=32

This shows a sync issue event (wbt_lat) that exceeded it's time. wbt_stat
dumps the current read/write stats for that window, and wbt_step shows a
step down event where we now scale back writes. Each trace includes the
device, 259:0 in this case.

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2016-11-09 12:36:15 -07:00
parent cf43e6be86
commit e34cbd3074
4 changed files with 1054 additions and 0 deletions

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@ -24,3 +24,4 @@ obj-$(CONFIG_BLK_CMDLINE_PARSER) += cmdline-parser.o
obj-$(CONFIG_BLK_DEV_INTEGRITY) += bio-integrity.o blk-integrity.o t10-pi.o obj-$(CONFIG_BLK_DEV_INTEGRITY) += bio-integrity.o blk-integrity.o t10-pi.o
obj-$(CONFIG_BLK_MQ_PCI) += blk-mq-pci.o obj-$(CONFIG_BLK_MQ_PCI) += blk-mq-pci.o
obj-$(CONFIG_BLK_DEV_ZONED) += blk-zoned.o obj-$(CONFIG_BLK_DEV_ZONED) += blk-zoned.o
obj-$(CONFIG_BLK_WBT) += blk-wbt.o

735
block/blk-wbt.c Normal file
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@ -0,0 +1,735 @@
/*
* buffered writeback throttling. loosely based on CoDel. We can't drop
* packets for IO scheduling, so the logic is something like this:
*
* - Monitor latencies in a defined window of time.
* - If the minimum latency in the above window exceeds some target, increment
* scaling step and scale down queue depth by a factor of 2x. The monitoring
* window is then shrunk to 100 / sqrt(scaling step + 1).
* - For any window where we don't have solid data on what the latencies
* look like, retain status quo.
* - If latencies look good, decrement scaling step.
* - If we're only doing writes, allow the scaling step to go negative. This
* will temporarily boost write performance, snapping back to a stable
* scaling step of 0 if reads show up or the heavy writers finish. Unlike
* positive scaling steps where we shrink the monitoring window, a negative
* scaling step retains the default step==0 window size.
*
* Copyright (C) 2016 Jens Axboe
*
*/
#include <linux/kernel.h>
#include <linux/blk_types.h>
#include <linux/slab.h>
#include <linux/backing-dev.h>
#include <linux/swap.h>
#include "blk-wbt.h"
#define CREATE_TRACE_POINTS
#include <trace/events/wbt.h>
enum {
/*
* Default setting, we'll scale up (to 75% of QD max) or down (min 1)
* from here depending on device stats
*/
RWB_DEF_DEPTH = 16,
/*
* 100msec window
*/
RWB_WINDOW_NSEC = 100 * 1000 * 1000ULL,
/*
* Disregard stats, if we don't meet this minimum
*/
RWB_MIN_WRITE_SAMPLES = 3,
/*
* If we have this number of consecutive windows with not enough
* information to scale up or down, scale up.
*/
RWB_UNKNOWN_BUMP = 5,
};
static inline bool rwb_enabled(struct rq_wb *rwb)
{
return rwb && rwb->wb_normal != 0;
}
/*
* Increment 'v', if 'v' is below 'below'. Returns true if we succeeded,
* false if 'v' + 1 would be bigger than 'below'.
*/
static bool atomic_inc_below(atomic_t *v, int below)
{
int cur = atomic_read(v);
for (;;) {
int old;
if (cur >= below)
return false;
old = atomic_cmpxchg(v, cur, cur + 1);
if (old == cur)
break;
cur = old;
}
return true;
}
static void wb_timestamp(struct rq_wb *rwb, unsigned long *var)
{
if (rwb_enabled(rwb)) {
const unsigned long cur = jiffies;
if (cur != *var)
*var = cur;
}
}
/*
* If a task was rate throttled in balance_dirty_pages() within the last
* second or so, use that to indicate a higher cleaning rate.
*/
static bool wb_recent_wait(struct rq_wb *rwb)
{
struct bdi_writeback *wb = &rwb->bdi->wb;
return time_before(jiffies, wb->dirty_sleep + HZ);
}
static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb, bool is_kswapd)
{
return &rwb->rq_wait[is_kswapd];
}
static void rwb_wake_all(struct rq_wb *rwb)
{
int i;
for (i = 0; i < WBT_NUM_RWQ; i++) {
struct rq_wait *rqw = &rwb->rq_wait[i];
if (waitqueue_active(&rqw->wait))
wake_up_all(&rqw->wait);
}
}
void __wbt_done(struct rq_wb *rwb, enum wbt_flags wb_acct)
{
struct rq_wait *rqw;
int inflight, limit;
if (!(wb_acct & WBT_TRACKED))
return;
rqw = get_rq_wait(rwb, wb_acct & WBT_KSWAPD);
inflight = atomic_dec_return(&rqw->inflight);
/*
* wbt got disabled with IO in flight. Wake up any potential
* waiters, we don't have to do more than that.
*/
if (unlikely(!rwb_enabled(rwb))) {
rwb_wake_all(rwb);
return;
}
/*
* If the device does write back caching, drop further down
* before we wake people up.
*/
if (rwb->wc && !wb_recent_wait(rwb))
limit = 0;
else
limit = rwb->wb_normal;
/*
* Don't wake anyone up if we are above the normal limit.
*/
if (inflight && inflight >= limit)
return;
if (waitqueue_active(&rqw->wait)) {
int diff = limit - inflight;
if (!inflight || diff >= rwb->wb_background / 2)
wake_up_all(&rqw->wait);
}
}
/*
* Called on completion of a request. Note that it's also called when
* a request is merged, when the request gets freed.
*/
void wbt_done(struct rq_wb *rwb, struct blk_issue_stat *stat)
{
if (!rwb)
return;
if (!wbt_is_tracked(stat)) {
if (rwb->sync_cookie == stat) {
rwb->sync_issue = 0;
rwb->sync_cookie = NULL;
}
if (wbt_is_read(stat))
wb_timestamp(rwb, &rwb->last_comp);
wbt_clear_state(stat);
} else {
WARN_ON_ONCE(stat == rwb->sync_cookie);
__wbt_done(rwb, wbt_stat_to_mask(stat));
wbt_clear_state(stat);
}
}
/*
* Return true, if we can't increase the depth further by scaling
*/
static bool calc_wb_limits(struct rq_wb *rwb)
{
unsigned int depth;
bool ret = false;
if (!rwb->min_lat_nsec) {
rwb->wb_max = rwb->wb_normal = rwb->wb_background = 0;
return false;
}
/*
* For QD=1 devices, this is a special case. It's important for those
* to have one request ready when one completes, so force a depth of
* 2 for those devices. On the backend, it'll be a depth of 1 anyway,
* since the device can't have more than that in flight. If we're
* scaling down, then keep a setting of 1/1/1.
*/
if (rwb->queue_depth == 1) {
if (rwb->scale_step > 0)
rwb->wb_max = rwb->wb_normal = 1;
else {
rwb->wb_max = rwb->wb_normal = 2;
ret = true;
}
rwb->wb_background = 1;
} else {
/*
* scale_step == 0 is our default state. If we have suffered
* latency spikes, step will be > 0, and we shrink the
* allowed write depths. If step is < 0, we're only doing
* writes, and we allow a temporarily higher depth to
* increase performance.
*/
depth = min_t(unsigned int, RWB_DEF_DEPTH, rwb->queue_depth);
if (rwb->scale_step > 0)
depth = 1 + ((depth - 1) >> min(31, rwb->scale_step));
else if (rwb->scale_step < 0) {
unsigned int maxd = 3 * rwb->queue_depth / 4;
depth = 1 + ((depth - 1) << -rwb->scale_step);
if (depth > maxd) {
depth = maxd;
ret = true;
}
}
/*
* Set our max/normal/bg queue depths based on how far
* we have scaled down (->scale_step).
*/
rwb->wb_max = depth;
rwb->wb_normal = (rwb->wb_max + 1) / 2;
rwb->wb_background = (rwb->wb_max + 3) / 4;
}
return ret;
}
static bool inline stat_sample_valid(struct blk_rq_stat *stat)
{
/*
* We need at least one read sample, and a minimum of
* RWB_MIN_WRITE_SAMPLES. We require some write samples to know
* that it's writes impacting us, and not just some sole read on
* a device that is in a lower power state.
*/
return stat[0].nr_samples >= 1 &&
stat[1].nr_samples >= RWB_MIN_WRITE_SAMPLES;
}
static u64 rwb_sync_issue_lat(struct rq_wb *rwb)
{
u64 now, issue = ACCESS_ONCE(rwb->sync_issue);
if (!issue || !rwb->sync_cookie)
return 0;
now = ktime_to_ns(ktime_get());
return now - issue;
}
enum {
LAT_OK = 1,
LAT_UNKNOWN,
LAT_UNKNOWN_WRITES,
LAT_EXCEEDED,
};
static int __latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
{
u64 thislat;
/*
* If our stored sync issue exceeds the window size, or it
* exceeds our min target AND we haven't logged any entries,
* flag the latency as exceeded. wbt works off completion latencies,
* but for a flooded device, a single sync IO can take a long time
* to complete after being issued. If this time exceeds our
* monitoring window AND we didn't see any other completions in that
* window, then count that sync IO as a violation of the latency.
*/
thislat = rwb_sync_issue_lat(rwb);
if (thislat > rwb->cur_win_nsec ||
(thislat > rwb->min_lat_nsec && !stat[0].nr_samples)) {
trace_wbt_lat(rwb->bdi, thislat);
return LAT_EXCEEDED;
}
/*
* No read/write mix, if stat isn't valid
*/
if (!stat_sample_valid(stat)) {
/*
* If we had writes in this stat window and the window is
* current, we're only doing writes. If a task recently
* waited or still has writes in flights, consider us doing
* just writes as well.
*/
if ((stat[1].nr_samples && rwb->stat_ops->is_current(stat)) ||
wb_recent_wait(rwb) || wbt_inflight(rwb))
return LAT_UNKNOWN_WRITES;
return LAT_UNKNOWN;
}
/*
* If the 'min' latency exceeds our target, step down.
*/
if (stat[0].min > rwb->min_lat_nsec) {
trace_wbt_lat(rwb->bdi, stat[0].min);
trace_wbt_stat(rwb->bdi, stat);
return LAT_EXCEEDED;
}
if (rwb->scale_step)
trace_wbt_stat(rwb->bdi, stat);
return LAT_OK;
}
static int latency_exceeded(struct rq_wb *rwb)
{
struct blk_rq_stat stat[2];
rwb->stat_ops->get(rwb->ops_data, stat);
return __latency_exceeded(rwb, stat);
}
static void rwb_trace_step(struct rq_wb *rwb, const char *msg)
{
trace_wbt_step(rwb->bdi, msg, rwb->scale_step, rwb->cur_win_nsec,
rwb->wb_background, rwb->wb_normal, rwb->wb_max);
}
static void scale_up(struct rq_wb *rwb)
{
/*
* Hit max in previous round, stop here
*/
if (rwb->scaled_max)
return;
rwb->scale_step--;
rwb->unknown_cnt = 0;
rwb->stat_ops->clear(rwb->ops_data);
rwb->scaled_max = calc_wb_limits(rwb);
rwb_wake_all(rwb);
rwb_trace_step(rwb, "step up");
}
/*
* Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
* had a latency violation.
*/
static void scale_down(struct rq_wb *rwb, bool hard_throttle)
{
/*
* Stop scaling down when we've hit the limit. This also prevents
* ->scale_step from going to crazy values, if the device can't
* keep up.
*/
if (rwb->wb_max == 1)
return;
if (rwb->scale_step < 0 && hard_throttle)
rwb->scale_step = 0;
else
rwb->scale_step++;
rwb->scaled_max = false;
rwb->unknown_cnt = 0;
rwb->stat_ops->clear(rwb->ops_data);
calc_wb_limits(rwb);
rwb_trace_step(rwb, "step down");
}
static void rwb_arm_timer(struct rq_wb *rwb)
{
unsigned long expires;
if (rwb->scale_step > 0) {
/*
* We should speed this up, using some variant of a fast
* integer inverse square root calculation. Since we only do
* this for every window expiration, it's not a huge deal,
* though.
*/
rwb->cur_win_nsec = div_u64(rwb->win_nsec << 4,
int_sqrt((rwb->scale_step + 1) << 8));
} else {
/*
* For step < 0, we don't want to increase/decrease the
* window size.
*/
rwb->cur_win_nsec = rwb->win_nsec;
}
expires = jiffies + nsecs_to_jiffies(rwb->cur_win_nsec);
mod_timer(&rwb->window_timer, expires);
}
static void wb_timer_fn(unsigned long data)
{
struct rq_wb *rwb = (struct rq_wb *) data;
unsigned int inflight = wbt_inflight(rwb);
int status;
status = latency_exceeded(rwb);
trace_wbt_timer(rwb->bdi, status, rwb->scale_step, inflight);
/*
* If we exceeded the latency target, step down. If we did not,
* step one level up. If we don't know enough to say either exceeded
* or ok, then don't do anything.
*/
switch (status) {
case LAT_EXCEEDED:
scale_down(rwb, true);
break;
case LAT_OK:
scale_up(rwb);
break;
case LAT_UNKNOWN_WRITES:
/*
* We started a the center step, but don't have a valid
* read/write sample, but we do have writes going on.
* Allow step to go negative, to increase write perf.
*/
scale_up(rwb);
break;
case LAT_UNKNOWN:
if (++rwb->unknown_cnt < RWB_UNKNOWN_BUMP)
break;
/*
* We get here when previously scaled reduced depth, and we
* currently don't have a valid read/write sample. For that
* case, slowly return to center state (step == 0).
*/
if (rwb->scale_step > 0)
scale_up(rwb);
else if (rwb->scale_step < 0)
scale_down(rwb, false);
break;
default:
break;
}
/*
* Re-arm timer, if we have IO in flight
*/
if (rwb->scale_step || inflight)
rwb_arm_timer(rwb);
}
void wbt_update_limits(struct rq_wb *rwb)
{
rwb->scale_step = 0;
rwb->scaled_max = false;
calc_wb_limits(rwb);
rwb_wake_all(rwb);
}
static bool close_io(struct rq_wb *rwb)
{
const unsigned long now = jiffies;
return time_before(now, rwb->last_issue + HZ / 10) ||
time_before(now, rwb->last_comp + HZ / 10);
}
#define REQ_HIPRIO (REQ_SYNC | REQ_META | REQ_PRIO)
static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw)
{
unsigned int limit;
/*
* At this point we know it's a buffered write. If this is
* kswapd trying to free memory, or REQ_SYNC is set, set, then
* it's WB_SYNC_ALL writeback, and we'll use the max limit for
* that. If the write is marked as a background write, then use
* the idle limit, or go to normal if we haven't had competing
* IO for a bit.
*/
if ((rw & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd())
limit = rwb->wb_max;
else if ((rw & REQ_BACKGROUND) || close_io(rwb)) {
/*
* If less than 100ms since we completed unrelated IO,
* limit us to half the depth for background writeback.
*/
limit = rwb->wb_background;
} else
limit = rwb->wb_normal;
return limit;
}
static inline bool may_queue(struct rq_wb *rwb, struct rq_wait *rqw,
wait_queue_t *wait, unsigned long rw)
{
/*
* inc it here even if disabled, since we'll dec it at completion.
* this only happens if the task was sleeping in __wbt_wait(),
* and someone turned it off at the same time.
*/
if (!rwb_enabled(rwb)) {
atomic_inc(&rqw->inflight);
return true;
}
/*
* If the waitqueue is already active and we are not the next
* in line to be woken up, wait for our turn.
*/
if (waitqueue_active(&rqw->wait) &&
rqw->wait.task_list.next != &wait->task_list)
return false;
return atomic_inc_below(&rqw->inflight, get_limit(rwb, rw));
}
/*
* Block if we will exceed our limit, or if we are currently waiting for
* the timer to kick off queuing again.
*/
static void __wbt_wait(struct rq_wb *rwb, unsigned long rw, spinlock_t *lock)
{
struct rq_wait *rqw = get_rq_wait(rwb, current_is_kswapd());
DEFINE_WAIT(wait);
if (may_queue(rwb, rqw, &wait, rw))
return;
do {
prepare_to_wait_exclusive(&rqw->wait, &wait,
TASK_UNINTERRUPTIBLE);
if (may_queue(rwb, rqw, &wait, rw))
break;
if (lock)
spin_unlock_irq(lock);
io_schedule();
if (lock)
spin_lock_irq(lock);
} while (1);
finish_wait(&rqw->wait, &wait);
}
static inline bool wbt_should_throttle(struct rq_wb *rwb, struct bio *bio)
{
const int op = bio_op(bio);
/*
* If not a WRITE (or a discard), do nothing
*/
if (!(op == REQ_OP_WRITE || op == REQ_OP_DISCARD))
return false;
/*
* Don't throttle WRITE_ODIRECT
*/
if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) == (REQ_SYNC | REQ_IDLE))
return false;
return true;
}
/*
* Returns true if the IO request should be accounted, false if not.
* May sleep, if we have exceeded the writeback limits. Caller can pass
* in an irq held spinlock, if it holds one when calling this function.
* If we do sleep, we'll release and re-grab it.
*/
unsigned int wbt_wait(struct rq_wb *rwb, struct bio *bio, spinlock_t *lock)
{
unsigned int ret = 0;
if (!rwb_enabled(rwb))
return 0;
if (bio_op(bio) == REQ_OP_READ)
ret = WBT_READ;
if (!wbt_should_throttle(rwb, bio)) {
if (ret & WBT_READ)
wb_timestamp(rwb, &rwb->last_issue);
return ret;
}
__wbt_wait(rwb, bio->bi_opf, lock);
if (!timer_pending(&rwb->window_timer))
rwb_arm_timer(rwb);
if (current_is_kswapd())
ret |= WBT_KSWAPD;
return ret | WBT_TRACKED;
}
void wbt_issue(struct rq_wb *rwb, struct blk_issue_stat *stat)
{
if (!rwb_enabled(rwb))
return;
/*
* Track sync issue, in case it takes a long time to complete. Allows
* us to react quicker, if a sync IO takes a long time to complete.
* Note that this is just a hint. 'stat' can go away when the
* request completes, so it's important we never dereference it. We
* only use the address to compare with, which is why we store the
* sync_issue time locally.
*/
if (wbt_is_read(stat) && !rwb->sync_issue) {
rwb->sync_cookie = stat;
rwb->sync_issue = blk_stat_time(stat);
}
}
void wbt_requeue(struct rq_wb *rwb, struct blk_issue_stat *stat)
{
if (!rwb_enabled(rwb))
return;
if (stat == rwb->sync_cookie) {
rwb->sync_issue = 0;
rwb->sync_cookie = NULL;
}
}
void wbt_set_queue_depth(struct rq_wb *rwb, unsigned int depth)
{
if (rwb) {
rwb->queue_depth = depth;
wbt_update_limits(rwb);
}
}
void wbt_set_write_cache(struct rq_wb *rwb, bool write_cache_on)
{
if (rwb)
rwb->wc = write_cache_on;
}
void wbt_disable(struct rq_wb *rwb)
{
if (rwb) {
del_timer_sync(&rwb->window_timer);
rwb->win_nsec = rwb->min_lat_nsec = 0;
wbt_update_limits(rwb);
}
}
EXPORT_SYMBOL_GPL(wbt_disable);
int wbt_init(struct request_queue *q, struct wb_stat_ops *ops)
{
struct rq_wb *rwb;
int i;
/*
* For now, we depend on the stats window being larger than
* our monitoring window. Ensure that this isn't inadvertently
* violated.
*/
BUILD_BUG_ON(RWB_WINDOW_NSEC > BLK_STAT_NSEC);
BUILD_BUG_ON(WBT_NR_BITS > BLK_STAT_RES_BITS);
if (!ops->get || !ops->is_current || !ops->clear)
return -EINVAL;
rwb = kzalloc(sizeof(*rwb), GFP_KERNEL);
if (!rwb)
return -ENOMEM;
for (i = 0; i < WBT_NUM_RWQ; i++) {
atomic_set(&rwb->rq_wait[i].inflight, 0);
init_waitqueue_head(&rwb->rq_wait[i].wait);
}
setup_timer(&rwb->window_timer, wb_timer_fn, (unsigned long) rwb);
rwb->wc = 1;
rwb->queue_depth = RWB_DEF_DEPTH;
rwb->last_comp = rwb->last_issue = jiffies;
rwb->bdi = &q->backing_dev_info;
rwb->win_nsec = RWB_WINDOW_NSEC;
rwb->stat_ops = ops;
rwb->ops_data = q;
wbt_update_limits(rwb);
/*
* Assign rwb, and turn on stats tracking for this queue
*/
q->rq_wb = rwb;
blk_stat_enable(q);
if (blk_queue_nonrot(q))
rwb->min_lat_nsec = 2000000ULL;
else
rwb->min_lat_nsec = 75000000ULL;
wbt_set_queue_depth(rwb, blk_queue_depth(q));
wbt_set_write_cache(rwb, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
return 0;
}
void wbt_exit(struct request_queue *q)
{
struct rq_wb *rwb = q->rq_wb;
if (rwb) {
del_timer_sync(&rwb->window_timer);
q->rq_wb = NULL;
kfree(rwb);
}
}

165
block/blk-wbt.h Normal file
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@ -0,0 +1,165 @@
#ifndef WB_THROTTLE_H
#define WB_THROTTLE_H
#include <linux/kernel.h>
#include <linux/atomic.h>
#include <linux/wait.h>
#include <linux/timer.h>
#include <linux/ktime.h>
#include "blk-stat.h"
enum wbt_flags {
WBT_TRACKED = 1, /* write, tracked for throttling */
WBT_READ = 2, /* read */
WBT_KSWAPD = 4, /* write, from kswapd */
WBT_NR_BITS = 3, /* number of bits */
};
enum {
WBT_NUM_RWQ = 2,
};
static inline void wbt_clear_state(struct blk_issue_stat *stat)
{
stat->time &= BLK_STAT_TIME_MASK;
}
static inline enum wbt_flags wbt_stat_to_mask(struct blk_issue_stat *stat)
{
return (stat->time & BLK_STAT_MASK) >> BLK_STAT_SHIFT;
}
static inline void wbt_track(struct blk_issue_stat *stat, enum wbt_flags wb_acct)
{
stat->time |= ((u64) wb_acct) << BLK_STAT_SHIFT;
}
static inline bool wbt_is_tracked(struct blk_issue_stat *stat)
{
return (stat->time >> BLK_STAT_SHIFT) & WBT_TRACKED;
}
static inline bool wbt_is_read(struct blk_issue_stat *stat)
{
return (stat->time >> BLK_STAT_SHIFT) & WBT_READ;
}
struct wb_stat_ops {
void (*get)(void *, struct blk_rq_stat *);
bool (*is_current)(struct blk_rq_stat *);
void (*clear)(void *);
};
struct rq_wait {
wait_queue_head_t wait;
atomic_t inflight;
};
struct rq_wb {
/*
* Settings that govern how we throttle
*/
unsigned int wb_background; /* background writeback */
unsigned int wb_normal; /* normal writeback */
unsigned int wb_max; /* max throughput writeback */
int scale_step;
bool scaled_max;
/*
* Number of consecutive periods where we don't have enough
* information to make a firm scale up/down decision.
*/
unsigned int unknown_cnt;
u64 win_nsec; /* default window size */
u64 cur_win_nsec; /* current window size */
struct timer_list window_timer;
s64 sync_issue;
void *sync_cookie;
unsigned int wc;
unsigned int queue_depth;
unsigned long last_issue; /* last non-throttled issue */
unsigned long last_comp; /* last non-throttled comp */
unsigned long min_lat_nsec;
struct backing_dev_info *bdi;
struct rq_wait rq_wait[WBT_NUM_RWQ];
struct wb_stat_ops *stat_ops;
void *ops_data;
};
static inline unsigned int wbt_inflight(struct rq_wb *rwb)
{
unsigned int i, ret = 0;
for (i = 0; i < WBT_NUM_RWQ; i++)
ret += atomic_read(&rwb->rq_wait[i].inflight);
return ret;
}
struct backing_dev_info;
#ifdef CONFIG_BLK_WBT
void __wbt_done(struct rq_wb *, enum wbt_flags);
void wbt_done(struct rq_wb *, struct blk_issue_stat *);
enum wbt_flags wbt_wait(struct rq_wb *, struct bio *, spinlock_t *);
int wbt_init(struct request_queue *, struct wb_stat_ops *);
void wbt_exit(struct request_queue *);
void wbt_update_limits(struct rq_wb *);
void wbt_requeue(struct rq_wb *, struct blk_issue_stat *);
void wbt_issue(struct rq_wb *, struct blk_issue_stat *);
void wbt_disable(struct rq_wb *);
void wbt_set_queue_depth(struct rq_wb *, unsigned int);
void wbt_set_write_cache(struct rq_wb *, bool);
#else
static inline void __wbt_done(struct rq_wb *rwb, enum wbt_flags flags)
{
}
static inline void wbt_done(struct rq_wb *rwb, struct blk_issue_stat *stat)
{
}
static inline enum wbt_flags wbt_wait(struct rq_wb *rwb, struct bio *bio,
spinlock_t *lock)
{
return 0;
}
static inline int wbt_init(struct request_queue *q, struct wb_stat_ops *ops)
{
return -EINVAL;
}
static inline void wbt_exit(struct request_queue *q)
{
}
static inline void wbt_update_limits(struct rq_wb *rwb)
{
}
static inline void wbt_requeue(struct rq_wb *rwb, struct blk_issue_stat *stat)
{
}
static inline void wbt_issue(struct rq_wb *rwb, struct blk_issue_stat *stat)
{
}
static inline void wbt_disable(struct rq_wb *rwb)
{
}
static inline void wbt_set_queue_depth(struct rq_wb *rwb, unsigned int depth)
{
}
static inline void wbt_set_write_cache(struct rq_wb *rwb, bool wc)
{
}
#endif /* CONFIG_BLK_WBT */
#endif

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include/trace/events/wbt.h Normal file
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#undef TRACE_SYSTEM
#define TRACE_SYSTEM wbt
#if !defined(_TRACE_WBT_H) || defined(TRACE_HEADER_MULTI_READ)
#define _TRACE_WBT_H
#include <linux/tracepoint.h>
#include "../../../block/blk-wbt.h"
/**
* wbt_stat - trace stats for blk_wb
* @stat: array of read/write stats
*/
TRACE_EVENT(wbt_stat,
TP_PROTO(struct backing_dev_info *bdi, struct blk_rq_stat *stat),
TP_ARGS(bdi, stat),
TP_STRUCT__entry(
__array(char, name, 32)
__field(s64, rmean)
__field(u64, rmin)
__field(u64, rmax)
__field(s64, rnr_samples)
__field(s64, rtime)
__field(s64, wmean)
__field(u64, wmin)
__field(u64, wmax)
__field(s64, wnr_samples)
__field(s64, wtime)
),
TP_fast_assign(
strncpy(__entry->name, dev_name(bdi->dev), 32);
__entry->rmean = stat[0].mean;
__entry->rmin = stat[0].min;
__entry->rmax = stat[0].max;
__entry->rnr_samples = stat[0].nr_samples;
__entry->wmean = stat[1].mean;
__entry->wmin = stat[1].min;
__entry->wmax = stat[1].max;
__entry->wnr_samples = stat[1].nr_samples;
),
TP_printk("%s: rmean=%llu, rmin=%llu, rmax=%llu, rsamples=%llu, "
"wmean=%llu, wmin=%llu, wmax=%llu, wsamples=%llu\n",
__entry->name, __entry->rmean, __entry->rmin, __entry->rmax,
__entry->rnr_samples, __entry->wmean, __entry->wmin,
__entry->wmax, __entry->wnr_samples)
);
/**
* wbt_lat - trace latency event
* @lat: latency trigger
*/
TRACE_EVENT(wbt_lat,
TP_PROTO(struct backing_dev_info *bdi, unsigned long lat),
TP_ARGS(bdi, lat),
TP_STRUCT__entry(
__array(char, name, 32)
__field(unsigned long, lat)
),
TP_fast_assign(
strncpy(__entry->name, dev_name(bdi->dev), 32);
__entry->lat = div_u64(lat, 1000);
),
TP_printk("%s: latency %lluus\n", __entry->name,
(unsigned long long) __entry->lat)
);
/**
* wbt_step - trace wb event step
* @msg: context message
* @step: the current scale step count
* @window: the current monitoring window
* @bg: the current background queue limit
* @normal: the current normal writeback limit
* @max: the current max throughput writeback limit
*/
TRACE_EVENT(wbt_step,
TP_PROTO(struct backing_dev_info *bdi, const char *msg,
int step, unsigned long window, unsigned int bg,
unsigned int normal, unsigned int max),
TP_ARGS(bdi, msg, step, window, bg, normal, max),
TP_STRUCT__entry(
__array(char, name, 32)
__field(const char *, msg)
__field(int, step)
__field(unsigned long, window)
__field(unsigned int, bg)
__field(unsigned int, normal)
__field(unsigned int, max)
),
TP_fast_assign(
strncpy(__entry->name, dev_name(bdi->dev), 32);
__entry->msg = msg;
__entry->step = step;
__entry->window = div_u64(window, 1000);
__entry->bg = bg;
__entry->normal = normal;
__entry->max = max;
),
TP_printk("%s: %s: step=%d, window=%luus, background=%u, normal=%u, max=%u\n",
__entry->name, __entry->msg, __entry->step, __entry->window,
__entry->bg, __entry->normal, __entry->max)
);
/**
* wbt_timer - trace wb timer event
* @status: timer state status
* @step: the current scale step count
* @inflight: tracked writes inflight
*/
TRACE_EVENT(wbt_timer,
TP_PROTO(struct backing_dev_info *bdi, unsigned int status,
int step, unsigned int inflight),
TP_ARGS(bdi, status, step, inflight),
TP_STRUCT__entry(
__array(char, name, 32)
__field(unsigned int, status)
__field(int, step)
__field(unsigned int, inflight)
),
TP_fast_assign(
strncpy(__entry->name, dev_name(bdi->dev), 32);
__entry->status = status;
__entry->step = step;
__entry->inflight = inflight;
),
TP_printk("%s: status=%u, step=%d, inflight=%u\n", __entry->name,
__entry->status, __entry->step, __entry->inflight)
);
#endif /* _TRACE_WBT_H */
/* This part must be outside protection */
#include <trace/define_trace.h>