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charset=us-ascii Content-Disposition: inline Hello. On Thu, Mar 30, 2023 at 07:17:57PM +0000, Yosry Ahmed wrote: > static void __mem_cgroup_flush_stats(void) > { > - unsigned long flag; > - > - if (!spin_trylock_irqsave(&stats_flush_lock, flag)) > + /* > + * We always flush the entire tree, so concurrent flushers can just > + * skip. This avoids a thundering herd problem on the rstat global lock > + * from memcg flushers (e.g. reclaim, refault, etc). > + */ > + if (atomic_read(&stats_flush_ongoing) || > + atomic_xchg(&stats_flush_ongoing, 1)) > return; I'm curious about why this instead of if (atomic_xchg(&stats_flush_ongoing, 1)) return; Is that some microarchitectural cleverness? Thanks, Michal --pchdddtux2qbf53z Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTrXXag4J0QvXXBmkMkDQmsBEOquQUCZCxV6AAKCRAkDQmsBEOq ucctAP0QF3CXk51W8Pmcc0e8ZfVGikqKVH42APSyMXgCLEw4twD/ajlglQ+6Jt7N Lf+TNXVTCA0s8f9NI8huIwxn6NR+XQc= =Q0r7 -----END PGP SIGNATURE----- --pchdddtux2qbf53z--