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Tue, 07 Nov 2023 10:33:48 -0800 (PST) Received: from localhost ([2620:10d:c091:400::5:86b7]) by smtp.gmail.com with ESMTPSA id j2-20020a056214022200b00670f8570a24sm157124qvt.23.2023.11.07.10.33.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Nov 2023 10:33:47 -0800 (PST) Date: Tue, 7 Nov 2023 13:33:46 -0500 From: Johannes Weiner To: Hyeongtak Ji Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hyeongtak Ji Subject: Re: [PATCH] mm/vmscan: consider previously reclaimed pages in shrink_lruvec() Message-ID: <20231107183346.GA3789583@cmpxchg.org> References: <1691402476-4838-1-git-send-email-hyeongtak.ji@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1691402476-4838-1-git-send-email-hyeongtak.ji@gmail.com> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 399471C001B X-Stat-Signature: frecrx6sfsen4hwtuu9ykew15pg9ih8h X-HE-Tag: 1699382029-301381 X-HE-Meta: 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 BgzTOyTT 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.095868, 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, Aug 07, 2023 at 07:01:16PM +0900, Hyeongtak Ji wrote: > shrink_lruvec() currently ignores previously reclaimed pages in > scan_control->nr_reclaimed. This can lead shrink_lruvec() to reclaiming > more pages than expected. > > This patch fixes shrink_lruvec() to take into account the previously > reclaimed pages. Do you run into real world issues from this? The code has been like this for at least a decade. It's an intentional choice to ensure fairness across all visited cgroups. sc->nr_to_reclaim is 32 pages or less - it's only to guard against extreme overreclaim. But we want to make sure we reclaim a bit from all cgroups, rather than always hit the first one and then bail.