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block/blk-iocost: collect per-cpu latency stats over possible CPUs

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ioc_lat_stat() walks ioc->pcpu_stat with for_each_online_cpu() to
compute missed-ppm and rq_wait deltas.  An offlined CPU is skipped, so
its delta is dropped from the period and its last_* watermark is not
advanced; on re-online the next collection sees a delta spanning the
whole offline interval, corrupting the latency/vrate picture.

Fixes: 7caa47151a ("blkcg: implement blk-iocost")
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Reviewed-by: Yu Kuai <yukuai@fygo.io>
Link: https://patch.msgid.link/20260720093726.28965-4-cui.tao@linux.dev
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tao Cui
2026-07-20 17:37:25 +08:00
committed by Jens Axboe
parent e0698304bd
commit 4e050c5b92
1 changed files with 1 additions and 1 deletions
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block/blk-iocost.c
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@@ -1592,7 +1592,7 @@ static void ioc_lat_stat(struct ioc *ioc, u32 *missed_ppm_ar, u32 *rq_wait_pct_p
u64 rq_wait_ns = 0;
int cpu, rw;
for_each_online_cpu(cpu) {
for_each_possible_cpu(cpu) {
struct ioc_pcpu_stat *stat = per_cpu_ptr(ioc->pcpu_stat, cpu);
u64 this_rq_wait_ns;