[PATCH v8 3/4] blk-throttle: factor out code to calculate ios/bytes_allowed

Yu Kuai
2022-08-23T03:31:29Z

From: Yu Kuai <yukuai3-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>

No functional changes, new apis will be used in later patches to
calculate wait time for throttled bios when new configuration is
submitted.

Noted this patch also rename tg_with_in_iops/bps_limit() to
tg_within_iops/bps_limit().

Signed-off-by: Yu Kuai <yukuai3-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Acked-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
block/blk-throttle.c | 59 ++++++++++++++++++++++++++------------------
1 file changed, 35 insertions(+), 24 deletions(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 773a355d3838..757b620f0f2d 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -754,33 +754,20 @@ static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
tg->slice_start[rw], tg->slice_end[rw], jiffies);
}

-static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
- u32 iops_limit, unsigned long *wait)
+static unsigned int calculate_io_allowed(u32 iops_limit,
+ unsigned long jiffy_elapsed)
{
- bool rw = bio_data_dir(bio);
unsigned int io_allowed;
- unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
u64 tmp;

- if (iops_limit == UINT_MAX || bio_flagged(bio, BIO_IOPS_THROTTLED)) {
- if (wait)
- *wait = 0;
- return true;
- }
-
- jiffy_elapsed = jiffies - tg->slice_start[rw];
-
- /* Round up to the next throttle slice, wait time must be nonzero */
- jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
-
/*
- * jiffy_elapsed_rnd should not be a big value as minimum iops can be
+ * jiffy_elapsed should not be a big value as minimum iops can be
* 1 then at max jiffy elapsed should be equivalent of 1 second as we
* will allow dispatch after 1 second and after that slice should
* have been trimmed.
*/

- tmp = (u64)iops_limit * jiffy_elapsed_rnd;
+ tmp = (u64)iops_limit * jiffy_elapsed;
do_div(tmp, HZ);

if (tmp > UINT_MAX)
@@ -788,6 +775,32 @@ static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
else
io_allowed = tmp;

+ return io_allowed;
+}
+
+static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed)
+{
+ return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ);
+}
+
+static bool tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio,
+ u32 iops_limit, unsigned long *wait)
+{
+ bool rw = bio_data_dir(bio);
+ unsigned int io_allowed;
+ unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
+
+ if (iops_limit == UINT_MAX || bio_flagged(bio, BIO_IOPS_THROTTLED)) {
+ if (wait)
+ *wait = 0;
+ return true;
+ }
+
+ jiffy_elapsed = jiffies - tg->slice_start[rw];
+
+ /* Round up to the next throttle slice, wait time must be nonzero */
+ jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
+ io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd);
if (tg->io_disp[rw] + 1 <= io_allowed) {
if (wait)
*wait = 0;
@@ -802,8 +815,8 @@ static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
return false;
}

-static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
- u64 bps_limit, unsigned long *wait)
+static bool tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio,
+ u64 bps_limit, unsigned long *wait)
{
bool rw = bio_data_dir(bio);
u64 bytes_allowed, extra_bytes;
@@ -824,9 +837,7 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
jiffy_elapsed_rnd = tg->td->throtl_slice;

jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
- bytes_allowed = mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed_rnd,
- (u64)HZ);
-
+ bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd);
if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {
if (wait)
*wait = 0;
@@ -895,8 +906,8 @@ 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_limit, &bps_wait) &&
- tg_with_in_iops_limit(tg, bio, iops_limit, &iops_wait)) {
+ if (tg_within_bps_limit(tg, bio, bps_limit, &bps_wait) &&
+ tg_within_iops_limit(tg, bio, iops_limit, &iops_wait)) {
if (wait)
*wait = 0;
return true;
--
2.31.1