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b=FDvOoiT495XTRGDVrFyuAeNU15WsyzV4yvBFsarf41CLypwwA2C7tzitZnevG9rRn K2Jey7ZWZXta1iFbZesEm7zhQ5EwLK1bekxB9thGCc11m9jjc7DLsQ9dV0vbRGbih7 C0sOlX44zD8uk09nA7RyayFYfqfgCdtZDdBpWQVM= Date: Thu, 3 Apr 2025 15:00:55 -0700 From: Andrew Morton To: Rik van Riel Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Vinay Banakar , liuye , Hugh Dickins , Mel Gorman , Yu Zhao , Shakeel Butt Subject: Re: [PATCH v2] mm/vmscan: batch TLB flush during memory reclaim Message-Id: <20250403150055.94a38bc7e6e3f618fbc23ddd@linux-foundation.org> In-Reply-To: <20250328142055.313916d1@fangorn> References: <20250328142055.313916d1@fangorn> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 4434F80013 X-Stat-Signature: qjpkhr3szozqmfrngsdc1wqfqbpawea5 X-Rspam-User: X-HE-Tag: 1743717657-802052 X-HE-Meta: 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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 Fri, 28 Mar 2025 14:20:55 -0400 Rik van Riel wrote: > The current implementation in shrink_folio_list() performs a full TLB > flush for every individual folio reclaimed. This causes unnecessary > overhead during memory reclaim. > > The current code: > 1. Clears PTEs and unmaps each page individually > 2. Performs a full TLB flush on every CPU the mm is running on > > The new code: > 1. Clears PTEs and unmaps each page individually > 2. Adds each unmapped page to pageout_folios > 3. Flushes the TLB once before procesing pageout_folios > > This reduces the number of TLB flushes issued by the memory reclaim > code by 1/N, where N is the number of mapped folios encountered in > the batch processed by shrink_folio_list. Were any runtime benefits observable?