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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id k7-20020a5d6287000000b002e463bd49e3sm1064660wru.66.2023.04.13.04.16.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 13 Apr 2023 04:16:24 -0700 (PDT) Message-ID: <0340c57b-dcec-42ba-eb6e-dd5599722ea4@redhat.com> Date: Thu, 13 Apr 2023 13:16:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Subject: Re: [PATCH v6 1/3] mm: vmscan: ignore non-LRU-based reclaim in memcg reclaim To: Yosry Ahmed , Andrew Morton , Alexander Viro , "Darrick J. Wong" , Christoph Lameter , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Matthew Wilcox (Oracle)" , Miaohe Lin , Johannes Weiner , Peter Xu , NeilBrown , Shakeel Butt , Michal Hocko , Yu Zhao , Dave Chinner , Tim Chen Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org References: <20230413104034.1086717-1-yosryahmed@google.com> <20230413104034.1086717-2-yosryahmed@google.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230413104034.1086717-2-yosryahmed@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 17A001C0005 X-Stat-Signature: jjjm3f15pabic13zhhxxxtcmji9aqp4n X-Rspam-User: X-HE-Tag: 1681384587-998081 X-HE-Meta: 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 +u456Eln 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 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 13.04.23 12:40, 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 > --- LGTM, hopefully the underestimation won't result in a real issue. Acked-by: David Hildenbrand -- Thanks, David / dhildenb