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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pGOYH-006KEV-Q0; Fri, 13 Jan 2023 18:13:17 +0000 Date: Fri, 13 Jan 2023 18:13:17 +0000 From: Matthew Wilcox To: Yin Fengwei Cc: linux-mm@kvack.org, dave.hansen@intel.com, tim.c.chen@intel.com, ying.huang@intel.com Subject: Re: [RFC PATCH] mm: populate multiple PTEs if file page is large folio Message-ID: References: <20230113163538.23412-1-fengwei.yin@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230113163538.23412-1-fengwei.yin@intel.com> X-Rspamd-Queue-Id: DB7E5A0015 X-Stat-Signature: tt9ayc94bnt93q4b63drht9m91e1bmch X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1673633588-524535 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: 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?