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[209.85.128.42]) by smtp.gmail.com with ESMTPSA id k24-20020aa7c398000000b0042dcac2afc6sm12465351edq.72.2022.06.08.08.57.22 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Jun 2022 08:57:22 -0700 (PDT) Received: by mail-wm1-f42.google.com with SMTP id z9so4358664wmf.3 for ; Wed, 08 Jun 2022 08:57:22 -0700 (PDT) X-Received: by 2002:a05:600c:4982:b0:39c:3c0d:437c with SMTP id h2-20020a05600c498200b0039c3c0d437cmr30759229wmp.38.1654703516902; Wed, 08 Jun 2022 08:51:56 -0700 (PDT) MIME-Version: 1.0 References: <20220518014632.922072-1-yuzhao@google.com> <20220518014632.922072-8-yuzhao@google.com> <20220607102135.GA32448@willie-the-truck> <20220607104358.GA32583@willie-the-truck> In-Reply-To: From: Linus Torvalds Date: Wed, 8 Jun 2022 08:51:40 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v11 07/14] mm: multi-gen LRU: exploit locality in rmap To: Barry Song <21cnbao@gmail.com> Cc: Yu Zhao , Will Deacon , Andrew Morton , Linux-MM , Andi Kleen , Aneesh Kumar , Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Peter Zijlstra , Tejun Heo , Vlastimil Babka , LAK , Linux Doc Mailing List , LKML , x86 , Kernel Page Reclaim v2 , Brian Geffon , Jan Alexander Steffens , Oleksandr Natalenko , Steven Barrett , Suleiman Souhlal , Daniel Byrne , Donald Carr , =?UTF-8?Q?Holger_Hoffst=C3=A4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain , huzhanyuan@oppo.com Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=RIC59qPh; dmarc=none; spf=pass (imf10.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.48 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 06EEAC0034 X-Rspam-User: X-Stat-Signature: iedy4f57kpy1nowx5mjr88py1hm9xw37 X-HE-Tag: 1654703843-714328 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 Tue, Jun 7, 2022 at 5:43 PM Barry Song <21cnbao@gmail.com> wrote: > > Given we used to have a flush for clear pte young in LRU, right now we are > moving to nop in almost all cases for the flush unless the address becomes > young exactly after look_around and before ptep_clear_flush_young_notify. > It means we are actually dropping flush. So the question is, were we > overcautious? we actually don't need the flush at all even without mglru? We stopped flushing the TLB on A bit clears on x86 back in 2014. See commit b13b1d2d8692 ("x86/mm: In the PTE swapout page reclaim case clear the accessed bit instead of flushing the TLB"). Linus