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Thu, 03 Apr 2025 09:47:42 -0700 (PDT) Date: Thu, 3 Apr 2025 12:47:41 -0400 From: Johannes Weiner To: Shakeel Butt Cc: Andrew Morton , Uladzislau Rezki , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH] memcg: vmalloc: simplify MEMCG_VMALLOC updates Message-ID: <20250403164741.GB368504@cmpxchg.org> References: <20250403053326.26860-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250403053326.26860-1-shakeel.butt@linux.dev> X-Rspamd-Server: rspam01 X-Stat-Signature: qjdkf9f9k8e7pnz5i7d8ph3u87sfaekk X-Rspam-User: X-Rspamd-Queue-Id: 059282000D X-HE-Tag: 1743698863-953707 X-HE-Meta: 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 rcr7HvAE 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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: List-Subscribe: List-Unsubscribe: On Wed, Apr 02, 2025 at 10:33:26PM -0700, Shakeel Butt wrote: > The vmalloc region can either be charged to a single memcg or none. At > the moment kernel traverses all the pages backing the vmalloc region to > update the MEMCG_VMALLOC stat. However there is no need to look at all > the pages as all those pages will be charged to a single memcg or none. > Simplify the MEMCG_VMALLOC update by just looking at the first page of > the vmalloc region. > > Signed-off-by: Shakeel Butt It's definitely pointless to handle each page with the stat being per-cgroup only. But I do wonder why it's not a regular vmstat item. There is no real reason it *should* be a private memcg stat, is there?