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blk-throttle: Avoid calculating bps/iops limitation repeatedly 

The tg_may_dispatch() will call tg_with_in_bps_limit() and
tg_with_in_iops_limit() to check if we can dispatch a bio or
not, which will calculate bps/iops limitation multiple times.
But tg_may_dispatch() is always called under queue lock, which
means the bps/iops limitation will not change in tg_may_dispatch().

So we can calculate the bps/iops limitation only once, and pass
them to tg_with_in_bps_limit() and tg_with_in_iops_limit() to
avoid calculating bps/iops limitation repeatedly.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Baolin Wang 2020-09-07 16:10:16 +08:00 committed by Jens Axboe
parent e675df2adc
commit 4599ea49d4
1 changed files with 10 additions and 9 deletions
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19
block/blk-throttle.c
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@ -894,7 +894,7 @@ static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
}
static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
unsigned long *wait)
u32 iops_limit, unsigned long *wait)
{
bool rw = bio_data_dir(bio);
unsigned int io_allowed;
@ -913,7 +913,7 @@ static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
* have been trimmed.
*/
tmp = (u64)tg_iops_limit(tg, rw) * jiffy_elapsed_rnd;
tmp = (u64)iops_limit * jiffy_elapsed_rnd;
do_div(tmp, HZ);
if (tmp > UINT_MAX)
@ -936,7 +936,7 @@ static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
}
static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
unsigned long *wait)
u64 bps_limit, unsigned long *wait)
{
bool rw = bio_data_dir(bio);
u64 bytes_allowed, extra_bytes, tmp;
@ -951,7 +951,7 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
tmp = tg_bps_limit(tg, rw) * jiffy_elapsed_rnd;
tmp = bps_limit * jiffy_elapsed_rnd;
do_div(tmp, HZ);
bytes_allowed = tmp;
@ -963,7 +963,7 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
/* Calc approx time to dispatch */
extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
jiffy_wait = div64_u64(extra_bytes * HZ, tg_bps_limit(tg, rw));
jiffy_wait = div64_u64(extra_bytes * HZ, bps_limit);
if (!jiffy_wait)
jiffy_wait = 1;
@ -987,6 +987,8 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
{
bool rw = bio_data_dir(bio);
unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
u64 bps_limit = tg_bps_limit(tg, rw);
u32 iops_limit = tg_iops_limit(tg, rw);
/*
* Currently whole state machine of group depends on first bio
@ -998,8 +1000,7 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
/* If tg->bps = -1, then BW is unlimited */
if (tg_bps_limit(tg, rw) == U64_MAX &&
tg_iops_limit(tg, rw) == UINT_MAX) {
if (bps_limit == U64_MAX && iops_limit == UINT_MAX) {
if (wait)
*wait = 0;
return true;
@ -1021,8 +1022,8 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
jiffies + tg->td->throtl_slice);
}
if (tg_with_in_bps_limit(tg, bio, &bps_wait) &&
tg_with_in_iops_limit(tg, bio, &iops_wait)) {
if (tg_with_in_bps_limit(tg, bio, bps_limit, &bps_wait) &&
tg_with_in_iops_limit(tg, bio, iops_limit, &iops_wait)) {
if (wait)
*wait = 0;
return true;