Messages in this thread | | | Date | Fri, 14 Apr 2023 10:59:26 +0800 | From | Aaron Lu <> | Subject | Re: [RFC PATCH v5] sched: Fix performance regression introduced by mm_cid |
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On Thu, Apr 13, 2023 at 11:11:14AM -0400, Mathieu Desnoyers wrote: > On 2023-04-13 10:37, Aaron Lu wrote: > > On Thu, Apr 13, 2023 at 10:02:48AM -0400, Mathieu Desnoyers wrote: > > > Introduce per-mm/cpu current concurrency id (mm_cid) to fix a PostgreSQL > > > sysbench regression reported by Aaron Lu. > > Initial test using postgres_sysbench showed the lock contention is gone :-) > > Will check how it affects hackbench tomorrow. > > That's good news! Not unexpected though. > > One thing to look closely at is whether it's just that the qspinlocks are > gone from the profiles but replaced by time spent in __mm_cid_get() due to > cache-line bouncing of find-first-zero/test-and-set on the per-mm cid > bitmap.
Found the below two appeared in profile when using cid as keyword, full profile attached for your reference.
# Children Self Shared Object Symbol 0.97% 0.62% [kernel.vmlinux] [k] sched_mm_cid_migrate_from 0.48% 0.47% [kernel.vmlinux] [k] mm_cid_get
Thanks, Aaron [unhandled content-type:application/gzip] | |