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Mon, 14 Aug 2023 17:47:57 -0700 (PDT) Received: from localhost ([2620:10d:c090:400::5:93bd]) by smtp.gmail.com with ESMTPSA id c9-20020a17090aa60900b00260a5ecd273sm8464607pjq.1.2023.08.14.17.47.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Aug 2023 17:47:56 -0700 (PDT) Date: Mon, 14 Aug 2023 14:47:55 -1000 From: Tejun Heo To: Yosry Ahmed Cc: Michal Hocko , Shakeel Butt , Johannes Weiner , Roman Gushchin , Andrew Morton , Muchun Song , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: memcg: provide accurate stats for userspace reads Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 732CE1C0013 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: xf5iqapb7xhbxerqga656rrcn5rjo99n X-HE-Tag: 1692060478-810102 X-HE-Meta: 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 UxnaGmlP 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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: Hello, On Mon, Aug 14, 2023 at 05:39:15PM -0700, Yosry Ahmed wrote: > I believe dropping unified flushing, if possible of course, may fix > both problems. Yeah, flushing the whole tree for every stat read will push up the big O complexity of the operation. It shouldn't be too bad because only what's updated since the last read will need flushing but if you have a really big machine with a lot of constantly active cgroups, you're still gonna feel it. So, yeah, drop that and switch the global lock to mutex and we should all be good? Thanks. -- tejun