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
parent
cf43e6be86
commit
e34cbd3074
@ -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-$(CONFIG_BLK_MQ_PCI) += blk-mq-pci.o
|
||||
obj-$(CONFIG_BLK_DEV_ZONED) += blk-zoned.o
|
||||
obj-$(CONFIG_BLK_WBT) += blk-wbt.o
|
||||
|
||||
735
block/blk-wbt.c
Normal file
735
block/blk-wbt.c
Normal file
@ -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
165
block/blk-wbt.h
Normal file
@ -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
|
||||
153
include/trace/events/wbt.h
Normal file
153
include/trace/events/wbt.h
Normal file
@ -0,0 +1,153 @@
|
||||
#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>
|
||||
Loading…
Reference in New Issue
Block a user