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AJvYcCV/nKZWl8VexkPBeJ6qtTE8IM8pFEeqyPdz7kMADGNKLd7U7LfbIdi0g7TQWoJpvIhyNo/AU8J7RuHxmNFf6/U0dxY= X-Gm-Message-State: AOJu0YzbsvdimTl4ecVWD6sJ/cfbSm+BTVSWZDSdMuzumzRwBJTNqexg jOhArQrOS+7fPn+ShDh8xVHnysuSebvNK3kEnCQAfXAnLsJ5rMGeKwM17ZSfGDU8GoVWuWGLndN 1roaKbg23cyo72jpMm2OuqXwEHc060Mb836fu X-Google-Smtp-Source: AGHT+IHaoPMigFap9qR56mDK6IoGtW0CNZrr495O28d2oa2CU+qgAxuG5JrPxUlJnGEnR0Odtvd35E9w1QRml/F5ldY= X-Received: by 2002:a17:907:7e8b:b0:a59:bfab:b254 with SMTP id qb11-20020a1709077e8b00b00a59bfabb254mr4113478ejc.64.1715021599491; Mon, 06 May 2024 11:53:19 -0700 (PDT) MIME-Version: 1.0 References: <20240506170024.202111-1-yosryahmed@google.com> In-Reply-To: From: Yosry Ahmed Date: Mon, 6 May 2024 11:52:40 -0700 Message-ID: Subject: Re: [PATCH] mm: do not update memcg stats for NR_{FILE/SHMEM}_PMDMAPPED To: David Hildenbrand Cc: Andrew Morton , Shakeel Butt , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+9319a4268a640e26b72b@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 485C6180003 X-Stat-Signature: sywg1pdugqpztyw3iu67zks4fsakcsan X-Rspam-User: X-HE-Tag: 1715021600-751468 X-HE-Meta: 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 Zn5I3yf7 MdVVqAGRLENy1Gniiq3RqKcJk8s06W3t4ENiwe4RpMYLYdPGm+8l8KTetDuazoXeRIPwBFfztmG7iUJwhw85jxrbAIe7+Vuh5LwbhgXpJiccF9yetMZAFfNi4HtAeb1SdfGB6PyOwrMPfK7bUsfXAb+rYaenZgxtvOqNaZ4+1eztR5F57aXEsrEDedjXGooWbeEXhUuG1vq9vTbbyjSu5ORVPXoMkZjYCKau38ZLENApT50kuWCPg2ma5C+Wbx4Tdkmy9DBgqyhxtO9S3E+abCMhIEGOWP4IIH8NUJif/EPmyHEXeWSFNkS7hZG2wEe1cTFZOb5zaIuiWNyChrwPHVNX4uICvp5/iVOR5gh9+zvVTXoG/gAoWi3CtG0K1mrVGi8IMiYYz4hEAskc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000060, 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 Mon, May 6, 2024 at 11:35=E2=80=AFAM David Hildenbrand wrote: > > On 06.05.24 19:00, Yosry Ahmed wrote: > > Do not use __lruvec_stat_mod_folio() when updating NR_FILE_PMDMAPPED an= d > > NR_SHMEM_PMDMAPPED as these stats are not maintained per-memcg. Use > > __mod_node_page_state() instead, which updates the global per-node stat= s > > only. > > What's the effect of this? IIUC, it's been that way forever, no? Yes, but it has been the case that all the NR_VM_EVENT_ITEMS stats were maintained per-memcg, although some of those fields are not exposed anywhere. Shakeel recently added commit14e0f6c957e39 ("memcg: reduce memory for the lruvec and memcg stats"), which changed this such that we only maintain the stats we actually expose per-memcg (via a translation table). He also added commit 514462bbe927b ("memcg: warn for unexpected events and stats"), which warns if we try to update a stat per-memcg that we do not maintain per-memcg (i.e. the warning firing here). The goal is to make sure the translation table has all the stats it needs to have. Both of these commits were just merged today into mm-stable, hence the need for the fix now. It is the warning working as intended. No Fixes or CC stable are needed, but if necessary I would think: Fixes: 514462bbe927b ("memcg: warn for unexpected events and stats") , because without the warning, the stat update will just be ignored. So if anything the warning should have been added *after* this was fixed up. > > Fixes: ? > > Do we want to CC stable? > > > -- > Cheers, > > David / dhildenb >