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[209.85.167.49]) by smtp.gmail.com with ESMTPSA id b11-20020a19670b000000b0044a385058acsm459872lfc.187.2022.04.15.14.43.02 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 Apr 2022 14:43:02 -0700 (PDT) Received: by mail-lf1-f49.google.com with SMTP id g19so1882634lfv.2 for ; Fri, 15 Apr 2022 14:43:02 -0700 (PDT) X-Received: by 2002:a2e:a78d:0:b0:24b:62bc:28ab with SMTP id c13-20020a2ea78d000000b0024b62bc28abmr551675ljf.164.1650058628048; Fri, 15 Apr 2022 14:37:08 -0700 (PDT) MIME-Version: 1.0 References: <20220407031525.2368067-1-yuzhao@google.com> <20220407031525.2368067-9-yuzhao@google.com> <20220411191621.0378467ad99ebc822d5ad005@linux-foundation.org> <20220414185654.e7150bcbe859e0dd4b9c61af@linux-foundation.org> <20220415121521.764a88dda55ae8c676ad26b0@linux-foundation.org> <20220415143220.cc37b0b0a368ed2bf2a821f8@linux-foundation.org> In-Reply-To: <20220415143220.cc37b0b0a368ed2bf2a821f8@linux-foundation.org> From: Linus Torvalds Date: Fri, 15 Apr 2022 14:36:51 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v10 08/14] mm: multi-gen LRU: support page table walks To: Andrew Morton Cc: Yu Zhao , Justin Forbes , 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-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: D3EDEC0003 X-Rspam-User: Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=Gq2Vs1cF; spf=pass (imf22.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.167.47 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=none X-Stat-Signature: oktahpigbkgyji515io66uei95wh6asq X-HE-Tag: 1650058984-923119 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 Fri, Apr 15, 2022 at 2:32 PM Andrew Morton wrote: > > We could create a new MM-developer-only assertion. Might even call it > MM_BUG_ON(). With compile-time enablement but perhaps not a runtime > switch. .. or VM_BUG_ON() could just become a WARN_ON_ONCE(). Which it should be anyway - since the code has to be written to continue after that BUG_ON() anyway. There is absolutely _zero_ advantage to killing the machine. If you want to be notified about "this must not happen", then WARN_ON_ONCE() is the right thing to use. BUG_ON() is basically always the wrong thing to do. Linus