Hi,
在 2025/04/14 10:32, Ming Lei 写道:
On Sat, Apr 12, 2025 at 08:37:28AM +0800, Yu Kuai wrote:
Hi,
在 2025/04/11 23:01, Ming Lei 写道:
On Fri, Apr 11, 2025 at 10:53:12AM +0800, Yu Kuai wrote:
Hi, Ming
在 2025/03/05 12:31, Ming Lei 写道:
Now ->carryover_bytes[] and ->carryover_ios[] only covers limit/config
update.
Actually the carryover bytes/ios can be carried to ->bytes_disp[] and
->io_disp[] directly, since the carryover is one-shot thing and only valid
in current slice.
Then we can remove the two fields and simplify code much.
Type of ->bytes_disp[] and ->io_disp[] has to change as signed because the
two fields may become negative when updating limits or config, but both are
big enough for holding bytes/ios dispatched in single slice
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
Cc: Yu Kuai <yukuai3@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-throttle.c | 49 +++++++++++++++++++-------------------------
block/blk-throttle.h | 4 ++--
2 files changed, 23 insertions(+), 30 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 7271aee94faf..91dab43c65ab 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -478,8 +478,6 @@ static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
{
tg->bytes_disp[rw] = 0;
tg->io_disp[rw] = 0;
- tg->carryover_bytes[rw] = 0;
- tg->carryover_ios[rw] = 0;
/*
* Previous slice has expired. We must have trimmed it after last
@@ -498,16 +496,14 @@ static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
}
static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw,
- bool clear_carryover)
+ bool clear)
{
- tg->bytes_disp[rw] = 0;
- tg->io_disp[rw] = 0;
+ if (clear) {
+ tg->bytes_disp[rw] = 0;
+ tg->io_disp[rw] = 0;
+ }
tg->slice_start[rw] = jiffies;
tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
- if (clear_carryover) {
- tg->carryover_bytes[rw] = 0;
- tg->carryover_ios[rw] = 0;
- }
throtl_log(&tg->service_queue,
"[%c] new slice start=%lu end=%lu jiffies=%lu",
@@ -617,20 +613,16 @@ static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
*/
time_elapsed -= tg->td->throtl_slice;
bytes_trim = calculate_bytes_allowed(tg_bps_limit(tg, rw),
- time_elapsed) +
- tg->carryover_bytes[rw];
- io_trim = calculate_io_allowed(tg_iops_limit(tg, rw), time_elapsed) +
- tg->carryover_ios[rw];
+ time_elapsed);
+ io_trim = calculate_io_allowed(tg_iops_limit(tg, rw), time_elapsed);
if (bytes_trim <= 0 && io_trim <= 0)
return;
- tg->carryover_bytes[rw] = 0;
if ((long long)tg->bytes_disp[rw] >= bytes_trim)
tg->bytes_disp[rw] -= bytes_trim;
else
tg->bytes_disp[rw] = 0;
- tg->carryover_ios[rw] = 0;
if ((int)tg->io_disp[rw] >= io_trim)
tg->io_disp[rw] -= io_trim;
else
@@ -645,7 +637,8 @@ static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
jiffies);
}
-static void __tg_update_carryover(struct throtl_grp *tg, bool rw)
+static void __tg_update_carryover(struct throtl_grp *tg, bool rw,
+ long long *bytes, int *ios)
{
unsigned long jiffy_elapsed = jiffies - tg->slice_start[rw];
u64 bps_limit = tg_bps_limit(tg, rw);
@@ -658,26 +651,28 @@ static void __tg_update_carryover(struct throtl_grp *tg, bool rw)
* configuration.
*/
if (bps_limit != U64_MAX)
- tg->carryover_bytes[rw] +=
- calculate_bytes_allowed(bps_limit, jiffy_elapsed) -
+ *bytes = calculate_bytes_allowed(bps_limit, jiffy_elapsed) -
tg->bytes_disp[rw];
if (iops_limit != UINT_MAX)
- tg->carryover_ios[rw] +=
- calculate_io_allowed(iops_limit, jiffy_elapsed) -
+ *ios = calculate_io_allowed(iops_limit, jiffy_elapsed) -
tg->io_disp[rw];
+ tg->bytes_disp[rw] -= *bytes;
+ tg->io_disp[rw] -= *ios;
This patch is applied before I get a chance to review. :( I think the
above update should be:
oops, your review period takes too long(> 1 month), :-(
Yes, I just didn't review in detail when I see this set is applied...
tg->bytes_disp[rw] = -*bytes;
tg->io_disp[rw] = -*ios;
I think the above is wrong since it simply override the existed dispatched
bytes/ios.
The calculation can be understood from two ways:
1) delta = calculate_bytes_allowed(bps_limit, jiffy_elapsed) - tg->bytes_disp[rw];
`delta` represents difference between theoretical and actual dispatch bytes.
If `delta` > 0, it means we dispatch too less in past, and we have to subtract
`delta` from ->bytes_disp, so that in future we can dispatch more.
But the problem is that in this patch, slice_start is set to *jiffies*,
keep the old disp filed that is between old slice_start to jiffies does
not make sense.
Similar with 'delta < 0'.
2) from consumer viewpoint:
tg_within_bps_limit(): patched
...
bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd);
if (bytes_allowed > 0 && tg->bytes_disp[rw] + bio_size <= bytes_allowed)
...
tg_within_bps_limit(): before patched
...
bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) +
tg->carryover_bytes[rw];
if (bytes_allowed > 0 && tg->bytes_disp[rw] + bio_size <= bytes_allowed)
...
So if `delta` is subtracted from `bytes_allowed` in patched code, we should
subtract same bytes from ->byte_disp[] side for maintaining the relation.
In the original carryover calculation, bytes_disp is always set to 0,
while slice start is set to jiffies. Patched version actually will be
less than old version if bytes_disp is not 0;
Indeed, you are right, care to send one fix?
Sure, my colleague is working on this, if you don't mind. :)
I'll review internally first, if you don't mind.
Thanks,
Kuai
Otherwise, please let me know, and I can do it too.
Thanks,
Ming
.
