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bh=ep+VEVzB2LjGG2sSXIqcURnz0hHXFz0q/BHjes7wSDo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=TL10kdYa/xrkXT+RHNiLDPOvHfAvM7oDD+QzDNvnIQndNUPSqkpzchDDa1DaDn2OJ YbjEUKBxYIRZFDtwifwcCaD2tUa57BQtVEFtZWz2yhqe/lUJHgtc52rsywpau/YbsS nTFXY4E4bvC58v/fxR+j5K8E6EVfNkuAY9/t+rDo= Date: Mon, 13 Mar 2023 11:49:00 -0700 From: Andrew Morton To: Yin Fengwei Cc: linux-mm@kvack.org, willy@infradead.org, mike.kravetz@oracle.com, sidhartha.kumar@oracle.com, naoya.horiguchi@nec.com, jane.chu@oracle.com, david@redhat.com Subject: Re: [PATCH v4 0/5] batched remove rmap in try_to_unmap_one() Message-Id: <20230313114900.96cfad6c3e4b684646f74e61@linux-foundation.org> In-Reply-To: <20230313124526.1207490-1-fengwei.yin@intel.com> References: <20230313124526.1207490-1-fengwei.yin@intel.com> 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: rspam07 X-Rspamd-Queue-Id: 08A6A40014 X-Rspam-User: X-Stat-Signature: 36df4rb4t6x6ryq1i3wmw66o1rk4enee X-HE-Tag: 1678733343-373805 X-HE-Meta: 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 MnNtK0S8 was4eb53ISro3hWpRVqZlEG+XXRC5f39XPuJQ8ilHHkStZHNHDfCLix50FSDh67tZxqGnNxQy1rxI4vLXmW/irwlU1C8rASqpPA1g0AOukxj10OM1oE4QNV1EyQqiNGVSUPq1HRg0gsXQqEOKTT33VU0h40Tv0ooGHZns99sB8jsOibKV25wrMMw0+CFJAWJb0GZYIVU2ILDz8JAPj5BU6jVkowQwLKA03HkuWo2NXQkeAb2UPNSrOG4eQRSnOHMdp4pRlq4cosqPbuwEJa8ah3LF5zgoGYCEZHaHDTD39HLFXsARLEMeLuWXRfR99pz9mtE80dO9OS9WF5zNlNF/u2p98HtNJRb5galSjrQ8ydzlKQetzksupRZA9yJQC8S4zI/jbNcT03q6yZXAzwU+zZV3KWBKIZ5gz5aK 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 Mon, 13 Mar 2023 20:45:21 +0800 Yin Fengwei wrote: > This series is trying to bring the batched rmap removing to > try_to_unmap_one(). It's expected that the batched rmap > removing bring performance gain than remove rmap per page. > > This series reconstruct the try_to_unmap_one() from: > loop: > clear and update PTE > unmap one page > goto loop > to: > loop: > clear and update PTE > goto loop > unmap the range of folio in one call > It is one step to always map/unmap the entire folio in one call. > Which can simplify the folio mapcount handling by avoid dealing > with each page map/unmap. > > ... > > For performance gain demonstration, changed the MADV_PAGEOUT not > to split the large folio for page cache and created a micro > benchmark mainly as following: Please remind me why it's necessary to patch the kernel to actually performance test this? And why it's proving so hard to demonstrate benefits in real-world workloads? (Yes, this was touched on in earlier discussion, but I do think these considerations should be spelled out in the [0/N] changelog). Thanks.