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Wed, 28 Jul 2021 02:36:06 +0000 Date: Tue, 27 Jul 2021 19:36:01 -0700 From: Roman Gushchin To: Shakeel Butt CC: Michal Hocko , Johannes Weiner , Andrew Morton , , , Subject: Re: [PATCH] memcg: cleanup racy sum avoidance code Message-ID: References: <20210728012243.3369123-1-shakeelb@google.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20210728012243.3369123-1-shakeelb@google.com> X-ClientProxiedBy: MWHPR14CA0019.namprd14.prod.outlook.com (2603:10b6:300:ae::29) To BYAPR15MB4136.namprd15.prod.outlook.com (2603:10b6:a03:96::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.dhcp.thefacebook.com (2620:10d:c090:400::5:c008) by MWHPR14CA0019.namprd14.prod.outlook.com (2603:10b6:300:ae::29) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4352.26 via Frontend Transport; Wed, 28 Jul 2021 02:36:05 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: f3c6a2b6-b959-44fe-6d3e-08d951707314 X-MS-TrafficTypeDiagnostic: BY5PR15MB4305: X-Microsoft-Antispam-PRVS: X-FB-Source: Internal X-MS-Oob-TLC-OOBClassifiers: OLM:8273; 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dkim=pass header.d=fb.com header.s=facebook header.b=C3sZLL54; dmarc=pass (policy=reject) header.from=fb.com; spf=pass (imf27.hostedemail.com: domain of "prvs=6843f525de=guro@fb.com" designates 67.231.145.42 as permitted sender) smtp.mailfrom="prvs=6843f525de=guro@fb.com" X-Stat-Signature: nnptf99i7auswrnmdyeyzs6pi6rufrkb X-HE-Tag: 1627439773-689453 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 Tue, Jul 27, 2021 at 06:22:43PM -0700, Shakeel Butt wrote: > We used to have per-cpu memcg and lruvec stats and the readers have to > traverse and sum the stats from each cpu. This summing was racy and may > expose transient negative values. So, an explicit check was added to > avoid such scenarios. Now these stats are moved to rstat infrastructure > and are no more per-cpu, so we can remove the fixup for transient > negative values. > > Signed-off-by: Shakeel Butt Acked-by: Roman Gushchin Thanks!