Re: [PATCH] ext4: isolate s_orphan_lock from read-mostly fields

[sashiko-bot@kernel.org]

> From: Jonas Zhou <jonaszhou@zhaoxin.com>
> 
> s_orphan_lock is modified by orphan-list operations, but currently shares
> a cache line with s_journal and s_ext4_flags.  The latter fields are read
> from common ext4 paths, so unrelated accesses can cause the line containing
> the lock to bounce between CPUs.
> 
> On a two-socket Intel Xeon Silver 4208 system with 16 workers, throughput
> improved by 4.6% for stress-ng.dnotify and 1.7% for stress-ng.unlink.  Perf
> c2c showed that HITM events on the affected fields decreased from 3,699 to
> 3,125 (-15.5%) for stress-ng.dnotify and from 1,368 to 571 (-58.3%) for
> stress-ng.unlink.  Remote HITM events decreased by 45.1% and 65.5%,
> respectively.  The journal/flags line had no remote HITM events after the
> change; the remaining remote HITM events were on the orphan-lock line.
> 
> Signed-off-by: Jonas Zhou <jonaszhou@zhaoxin.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260903021836.962624-1-jonaszhou-oc@zhaoxin.com?part=1