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Wed, 04 Oct 2023 12:46:31 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:753d]) by smtp.gmail.com with ESMTPSA id jr10-20020a05622a800a00b00403ff38d855sm1440504qtb.4.2023.10.04.12.46.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Oct 2023 12:46:31 -0700 (PDT) Date: Wed, 4 Oct 2023 15:46:30 -0400 From: Johannes Weiner To: Nhat Pham Cc: akpm@linux-foundation.org, riel@surriel.com, mhocko@kernel.org, roman.gushchin@linux.dev, shakeelb@google.com, muchun.song@linux.dev, tj@kernel.org, lizefan.x@bytedance.com, shuah@kernel.org, mike.kravetz@oracle.com, yosryahmed@google.com, fvdl@google.com, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [PATCH v2] memcontrol: only transfer the memcg data for migration Message-ID: <20231004194630.GC39112@cmpxchg.org> References: <20231004193622.900383-1-nphamcs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231004193622.900383-1-nphamcs@gmail.com> X-Rspamd-Queue-Id: 0EFCF80018 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 4pkku5k43df5w89mmds7rjtbehcm8b7c X-HE-Tag: 1696448792-101286 X-HE-Meta: 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 VrUSfg1V 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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 Wed, Oct 04, 2023 at 12:36:22PM -0700, Nhat Pham wrote: > For most migration use cases, only transfer the memcg data from the old > folio to the new folio, and clear the old folio's memcg data. No > charging and uncharging will be done. > > This shaves off some work on the migration path, and avoids the > temporary double charging of a folio during its migration. > > The only exception is replace_page_cache_folio(), which will use the old > mem_cgroup_migrate() (now renamed to mem_cgroup_replace_folio). In that > context, the isolation of the old page isn't quite as thorough as with > migration, so we cannot use our new implementation directly. > > This patch is the result of the following discussion on the new hugetlb > memcg accounting behavior: > > https://lore.kernel.org/lkml/20231003171329.GB314430@monkey/ > > This should be added as the second prep patch in the following series: > https://lore.kernel.org/all/20231003001828.2554080-1-nphamcs@gmail.com/ > (hugetlb memcg accounting) > > and should go right before the following patch: > hugetlb: memcg: account hugetlb-backed memory in memory controller > > Reported-by: Mike Kravetz > Closes: https://lore.kernel.org/lkml/20231003171329.GB314430@monkey/ These two tags shouldn't be here, but in the fixlet instead. This is the dependency patch. Otherwise looks good to me: > Suggested-by: Johannes Weiner > Signed-off-by: Nhat Pham Acked-by: Johannes Weiner