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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pk6G0-00GYSX-02; Wed, 05 Apr 2023 16:45:12 +0000 Date: Wed, 5 Apr 2023 17:45:11 +0100 From: Matthew Wilcox To: Qi Zheng Cc: akpm@linux-foundation.org, lstoakes@gmail.com, mgorman@suse.de, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] mm: swap: fix performance regression on sparsetruncate-tiny Message-ID: References: <20230405161854.6931-1-zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230405161854.6931-1-zhengqi.arch@bytedance.com> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 0930A4001A X-Stat-Signature: 56as6uuj7gqcskaxqw8oqakdb1w7fffu X-HE-Tag: 1680713121-561774 X-HE-Meta: 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 1NGt/xab IUBAT0SLpoB04sE6Id6m3ZGf8W4XDm6ltLDxWscOcdJOkeQP5ez44y0pEJS8hNZfYPen2o3pENqtvNrPMZxde0aY2D6UtMOx9G+g3fs9RAT/Y75mQWTAD/dZMCmMHDx3EaAGsdwd9GFM0Swy8QivXSNq2SVEbbLeCchbLLl6C4zAk4P+HZA5Sp7cKy0HTnT7v/9uRKDP7B99brDAk97zTqQPC1Mkp/xs/oE6zRSgcqMp8NSQtdo6IOhESzrQ0PACuVGr2cVf3G4ajikE= 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 Thu, Apr 06, 2023 at 12:18:53AM +0800, Qi Zheng wrote: > The ->percpu_pvec_drained was originally introduced by > commit d9ed0d08b6c6 ("mm: only drain per-cpu pagevecs once per > pagevec usage") to drain per-cpu pagevecs only once per pagevec > usage. But after converting the swap code to be more folio-based, > the commit c2bc16817aa0 ("mm/swap: add folio_batch_move_lru()") > breaks this logic, which would cause ->percpu_pvec_drained to be > reset to false, that means per-cpu pagevecs will be drained > multiple times per pagevec usage. My mistake. I didn't reaise that we'd need a folio_batch_reinit(), and indeed we didn't have one until 811561288397 (January 2023). I thought this usage of percpu_pvec_drained was going to be fine with being set to false each time. Thanks for showing I was wrong. > Fixes: c2bc16817aa0 ("mm/swap: add folio_batch_move_lru()") > Signed-off-by: Qi Zheng Reviewed-by: Matthew Wilcox (Oracle)