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[209.85.218.53]) by smtp.gmail.com with ESMTPSA id v8-20020a1709064e8800b006ef74044062sm5248885eju.16.2022.04.20.13.14.51 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Apr 2022 13:14:51 -0700 (PDT) Received: by mail-ej1-f53.google.com with SMTP id y10so5776429ejw.8 for ; Wed, 20 Apr 2022 13:14:51 -0700 (PDT) X-Received: by 2002:ac2:4203:0:b0:448:8053:d402 with SMTP id y3-20020ac24203000000b004488053d402mr15354025lfh.687.1650485251826; Wed, 20 Apr 2022 13:07:31 -0700 (PDT) MIME-Version: 1.0 References: <20220407031525.2368067-1-yuzhao@google.com> <20220407031525.2368067-6-yuzhao@google.com> <20220411191615.a34959bdcc25ef3f9c16a7ce@linux-foundation.org> <20220412070616.GT2731@worktop.programming.kicks-ass.net> In-Reply-To: From: Linus Torvalds Date: Wed, 20 Apr 2022 13:07:15 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v10 05/14] mm: multi-gen LRU: groundwork To: Yu Zhao Cc: Peter Zijlstra , Andrew Morton , Stephen Rothwell , Linux-MM , Andi Kleen , Aneesh Kumar , Barry Song <21cnbao@gmail.com>, Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Rik van Riel , Vlastimil Babka , Will Deacon , Ying Huang , Linux ARM , "open list:DOCUMENTATION" , linux-kernel , Kernel Page Reclaim v2 , "the arch/x86 maintainers" , 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 Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 7EBC540022 X-Stat-Signature: i9ypp1n3rdhucwzk696adc584a3xw4fo Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=PwJpWKVj; spf=pass (imf27.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.42 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=none X-HE-Tag: 1650485692-270563 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, Apr 19, 2022 at 5:39 PM Yu Zhao wrote: > > A related question: if I pass new = old to try_cmpxchg(), does it know > that and avoid an unnecessary atomic op? No. try_cmpxchg() basically translates directly to a cmpxchg instruction (on x86) with the return value being the eflags 'Z' bit. Linus