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Wong" , Christoph Lameter , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Matthew Wilcox (Oracle)" , Miaohe Lin , David Hildenbrand , Johannes Weiner , Peter Xu , NeilBrown , Shakeel Butt , Yu Zhao , Dave Chinner , Tim Chen , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v6 1/3] mm: vmscan: ignore non-LRU-based reclaim in memcg reclaim Message-ID: References: <20230413104034.1086717-1-yosryahmed@google.com> <20230413104034.1086717-2-yosryahmed@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230413104034.1086717-2-yosryahmed@google.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 8B37F1A0011 X-Stat-Signature: kg4jpass5xgzbfdbi3dq6hzkcsowynh9 X-HE-Tag: 1681460120-554433 X-HE-Meta: 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 DkwFoVKv ew8NecHFY8dhTAemHRDFX0tGwb09TaItPhPldwwvinuPtzXqcL5FGZNRt55xv2BM12mpaz+Ba1dE614wU8jtFKM/7v82pkKe2RLiG2yPrmyvXhmsl/zP34CJnP6DeAu2vSCA98LDKq5SKnRu+8zxJVkDOEyuCitInB2rgXQllImgTaXqAzPlpNfNC3Op6zVXSrbVNYksShllbfNCquQrX6BI62pTSh/P1w1IMjs3xkZs4Vqw+WZSqO+U1/uWysZS6ae3kjSmfWluvA+QTrzNiY1eOJAV6dXD7zVn9IJEdu8/fR9viYVNRe6g0D07MnFFsENXf 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: On Thu 13-04-23 10:40:32, Yosry Ahmed wrote: > We keep track of different types of reclaimed pages through > reclaim_state->reclaimed_slab, and we add them to the reported number > of reclaimed pages. For non-memcg reclaim, this makes sense. For memcg > reclaim, we have no clue if those pages are charged to the memcg under > reclaim. > > Slab pages are shared by different memcgs, so a freed slab page may have > only been partially charged to the memcg under reclaim. The same goes for > clean file pages from pruned inodes (on highmem systems) or xfs buffer > pages, there is no simple way to currently link them to the memcg under > reclaim. > > Stop reporting those freed pages as reclaimed pages during memcg reclaim. > This should make the return value of writing to memory.reclaim, and may > help reduce unnecessary reclaim retries during memcg charging. Writing to > memory.reclaim on the root memcg is considered as cgroup_reclaim(), but > for this case we want to include any freed pages, so use the > global_reclaim() check instead of !cgroup_reclaim(). > > Generally, this should make the return value of > try_to_free_mem_cgroup_pages() more accurate. In some limited cases (e.g. > freed a slab page that was mostly charged to the memcg under reclaim), > the return value of try_to_free_mem_cgroup_pages() can be underestimated, > but this should be fine. The freed pages will be uncharged anyway, and we > can charge the memcg the next time around as we usually do memcg reclaim > in a retry loop. > > Fixes: f2fe7b09a52b ("mm: memcg/slab: charge individual slab objects > instead of pages") > > Signed-off-by: Yosry Ahmed Acked-by: Michal Hocko -- Michal Hocko SUSE Labs