6.18-stable review patch. If anyone has any objections, please let me know.
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From: Guenter Roeck linux@roeck-us.net
[ Upstream commit f76581f9f1d29e32e120b0242974ba266e79de58 ]
Commit d61fcfa4bb18 ("blk-throttle: choose a small throtl_slice for SSD") introduced device type specific throttle slices if BLK_DEV_THROTTLING_LOW was enabled. Commit bf20ab538c81 ("blk-throttle: remove CONFIG_BLK_DEV_THROTTLING_LOW") removed support for BLK_DEV_THROTTLING_LOW, but left the device type specific throttle slices in place. This effectively changed throttling behavior on systems with SSD which now use a different and non-configurable slice time compared to non-SSD devices. Practical impact is that throughput tests with low configured throttle values (65536 bps) experience less than expected throughput on SSDs, presumably due to rounding errors associated with the small throttle slice time used for those devices. The same tests pass when setting the throttle values to 65536 * 4 = 262144 bps.
The original code sets the throttle slice time to DFL_THROTL_SLICE_HD if CONFIG_BLK_DEV_THROTTLING_LOW is disabled. Restore that code to fix the problem. With that, DFL_THROTL_SLICE_SSD is no longer necessary. Revert to the original code and re-introduce DFL_THROTL_SLICE to replace both DFL_THROTL_SLICE_HD and DFL_THROTL_SLICE_SSD. This effectively reverts commit d61fcfa4bb18 ("blk-throttle: choose a small throtl_slice for SSD").
While at it, also remove MAX_THROTL_SLICE since it is not used anymore.
Fixes: bf20ab538c81 ("blk-throttle: remove CONFIG_BLK_DEV_THROTTLING_LOW") Cc: Yu Kuai yukuai@kernel.org Cc: Tejun Heo tj@kernel.org Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Khazhismel Kumykov khazhy@google.com Reviewed-by: Yu Kuai yukuai@fnnas.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-throttle.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 2c5b64b1a724a..c19d052a8f2f1 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -22,9 +22,7 @@ #define THROTL_QUANTUM 32
/* Throttling is performed over a slice and after that slice is renewed */ -#define DFL_THROTL_SLICE_HD (HZ / 10) -#define DFL_THROTL_SLICE_SSD (HZ / 50) -#define MAX_THROTL_SLICE (HZ) +#define DFL_THROTL_SLICE (HZ / 10)
/* A workqueue to queue throttle related work */ static struct workqueue_struct *kthrotld_workqueue; @@ -1341,10 +1339,7 @@ static int blk_throtl_init(struct gendisk *disk) goto out; }
- if (blk_queue_nonrot(q)) - td->throtl_slice = DFL_THROTL_SLICE_SSD; - else - td->throtl_slice = DFL_THROTL_SLICE_HD; + td->throtl_slice = DFL_THROTL_SLICE; td->track_bio_latency = !queue_is_mq(q); if (!td->track_bio_latency) blk_stat_enable_accounting(q);