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charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20250226032258.234099-1-krisman@suse.de> X-Rspamd-Queue-Id: BCF9040039 X-Rspamd-Server: rspam08 X-Rspam-User: X-Stat-Signature: 7kpsw79fncym3i5k69ho1h7roksh6ddg X-HE-Tag: 1740657010-953281 X-HE-Meta: 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 L6GhOCeH YUYAKMJQQED+MLo0f8bNt0i9E0Ik634AcdxQS5Nif0h3eP/6t0+Jvp7gl9OkOE70b/BTEKRsCKYL2mcBiSGyykH/VTZjYQ9Pqh/tmaReV7rRykpO6C2Ifw1+JAeEWMIfhN1gLKpcouTpz7cIYJ0PsFSbA68rPjDgnWx4fE8WK0eMSIUsbNyR0uEx6PWOA0w1eu1enqUo7koOasiTlZknOW8aS9FEnQ/KxSMRXAS4ENHkvrd1lw0GdYj2GyBlH6kV1Qv1UsoL2A93+GqeiLjPsCgd7LRbIqG8IOJWSZrzNdQ5zoBSqE3am+e015MZnKz6d60jdNAt5Jqex+EpqNM6g3fptxodXIzg0lzNq4FUd5ZL3ozU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Feb 25, 2025 at 10:22:58PM -0500, Gabriel Krisman Bertazi wrote: > Commit 96a5c186efff ("mm/page_alloc.c: don't show protection in zone's > ->lowmem_reserve[] for empty zone") removes the protection of lower > zones from allocations targeting memory-less high zones. This had an > unintended impact on the pattern of reclaims because it makes the > high-zone-targeted allocation more likely to succeed in lower zones, > which adds pressure to said zones. I.e, the following corresponding > checks in zone_watermark_ok/zone_watermark_fast are less likely to > trigger: > > if (free_pages <= min + z->lowmem_reserve[highest_zoneidx]) > return false; > > As a result, we are observing an increase in reclaim and kswapd scans, > due to the increased pressure. This was initially observed as increased > latency in filesystem operations when benchmarking with fio on a machine > with some memory-less zones, but it has since been associated with > increased contention in locks related to memory reclaim. By reverting > this patch, the original performance was recovered on that machine. > > The original commit was introduced as a clarification of the > /proc/zoneinfo output, so it doesn't seem there are usecases depending > on it, making the revert a simple solution. > > Cc: Michal Hocko > Cc: Mel Gorman > Cc: Vlastimil Babka > Cc: Baoquan He > Fixes: 96a5c186efff ("mm/page_alloc.c: don't show protection in zone's ->lowmem_reserve[] for empty zone") > Signed-off-by: Gabriel Krisman Bertazi Acked-by: Mel Gorman -- Mel Gorman SUSE Labs