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[2003:cb:c708:f00:323e:5956:8da1:9237]) by smtp.gmail.com with ESMTPSA id m5-20020a05600c3b0500b003c6b7f5567csm18073324wms.0.2023.01.17.02.37.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Jan 2023 02:37:05 -0800 (PST) Message-ID: Date: Tue, 17 Jan 2023 11:37:05 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [RFC PATCH] mm: populate multiple PTEs if file page is large folio To: "Yin, Fengwei" , Matthew Wilcox Cc: linux-mm@kvack.org, dave.hansen@intel.com, tim.c.chen@intel.com, ying.huang@intel.com References: <20230113163538.23412-1-fengwei.yin@intel.com> <2100e7c9-2a5c-4c1a-6e22-9710a2b0c66f@intel.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <2100e7c9-2a5c-4c1a-6e22-9710a2b0c66f@intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: gkenycw7yypw1gauu1srft7z3juoyxsg X-Rspam-User: X-Rspamd-Queue-Id: 1B0C640013 X-Rspamd-Server: rspam06 X-HE-Tag: 1673951829-175927 X-HE-Meta: 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 d1vQ2XNi zXjrrkC/VZMEgB1GcjloMbgVHdaWlX/TFd9J3rDE/3FELGl5cZt+050TquMW3mlCZS3tFPb4Fxiceymt7+OpCadBig4+BLH7Yw1+Sn59YWlBQ2xJKv0mMcCmbvAgMOKXfQUYC/euynqxBW6U= 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 17.01.23 10:19, Yin, Fengwei wrote: > > > On 1/14/2023 2:13 AM, Matthew Wilcox wrote: >> On Sat, Jan 14, 2023 at 12:35:38AM +0800, Yin Fengwei wrote: >>> The page fault number can be reduced by batched PTEs population. >>> The batch size of PTEs population is not allowed to cross: >>> - page table boundaries >>> - vma range >>> - large folio size >>> - fault_around_bytes >> >> I find this patch very interesting. But is it really worth it? Most >> file-backed page faults are resolved through the ->map_pages() path >> which is almost always filemap_map_pages(), which does something >> fairly similar to this already. Do you have any performance numbers? >> > I tried the will-it-scale page_fault3: > https://github.com/antonblanchard/will-it-scale/blob/master/tests/page_fault3.c > with 96 processes on a test box with 48C/86T. > > The test result got about 3.75X better with 4.1X less page fault number > with this patch. > > But It's a micro benchmark which shows extreme friendly case to this patch. > > I didn't see observed performance gain with other workloads. I suppose > shared file write operations may not be common operations? Thanks. One question I have after reading "which does something fairly similar to this already", if both paths could be unified. -- Thanks, David / dhildenb