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[209.85.167.54]) by smtp.gmail.com with ESMTPSA id s11-20020a2e9c0b000000b0024ace83744asm386424lji.116.2022.04.15.14.37.18 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 Apr 2022 14:37:19 -0700 (PDT) Received: by mail-lf1-f54.google.com with SMTP id o2so15677465lfu.13 for ; Fri, 15 Apr 2022 14:37:18 -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" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9DBCFC433F5 for ; Fri, 15 Apr 2022 21:38:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=9iveqZ2bAWTy3u3lBmGcG6xF7T1+HVYRy9DC6ifRLAw=; b=KrU3+S6d5cxWlV naL1vtbsFnAHahpd9701MLQUVtd9hjfGkCDC2Ih+4w+V8oLCDgtWHm1Isi6vIBOqwZlo9dh/Nrys9 zlGIfSkGkgSBYRbMvUuQeJyG0OF4QbfYpRcXlOeKuwM1RJ0N8BBiggycFBjJc9y4KjKgxuNInfmvh lysM8D3dzf7q2Jk+TO+jRfKGs8xRQTUack1qMjkudbeGf75JS4pnAbD7HxhrIYtKAIvCB/o6HZFXf 2rYDz4+XnRMbhw0UphXWbXbI2+X0YpZZy9wyjl+jtwhtdZfy6v6wvAwZLqk1crXdgwc70imn7MwX0 nfkQ9RxB020ykV8+IolQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nfTd5-00BOe7-US; Fri, 15 Apr 2022 21:37:24 +0000 Received: from mail-ed1-x52a.google.com ([2a00:1450:4864:20::52a]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nfTd2-00BOcn-Mv for linux-arm-kernel@lists.infradead.org; Fri, 15 Apr 2022 21:37:22 +0000 Received: by mail-ed1-x52a.google.com with SMTP id c64so11119091edf.11 for ; Fri, 15 Apr 2022 14:37:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=lLriqQ645VZTKiVXonXX4zRxAjFhyB+B/84wbgqzXws=; b=Gq2Vs1cFahE54e4owDzXlpQ6dM9RqC+NMapopJ2Rgvnza5P4DZtfb948KXCZcASNMh Iezdw+NJsOwznSxZ1Bpo42TB6jsvbJqRWxbAc6bUJkl3zS3MuE5HboWtBp6hRyTXcZb5 RQkyzuR9gn2IlHUb49/bg4XA6i75eDo/o8CNc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=lLriqQ645VZTKiVXonXX4zRxAjFhyB+B/84wbgqzXws=; b=jcax5vAMdlFgn5QtIXrOhRBM2rBkRusrYbJLSXh5QpWfTyJr5csYGoNQg0ODdBMoYY gmz9iV/BEyOOWs5z/3MAvAhn1BG/DTXTjhU8QbnVHlvLXS2FaNxBCvYk8N2NyVY/aQ9U 3SVl5H3xudpdiFFm+vdLnB613VdsL/gXMirBcV3eVkBpPjlk1xBV1BRSO7liq2w73sd7 kDtGxOMZfU/MXyZTTgw0LtyaeS7Gv/fchqciVPl7GDK9xLoF51RN5q2/nbEsjpvt/VF4 In/gU/2gpO+ZkCnp+o1zJISIcTyO/34/D1lA4mzWt1wdOCs0OONVQZvjNCYT9pxMd5TZ vhtg== X-Gm-Message-State: AOAM530mf/L9ZR/M+Y0MxEt/xjqkwxnhMuJPkQHxn2WGbik0hJn3ktQz ix8HJgJdOid+ONcliw78mIhAuKnqYAkuI7HsJ7Y= X-Google-Smtp-Source: ABdhPJwQzc4SNbSTw0C6lxmZn3HL76LCLxfAINTZ3R+dVKXAaB6FuUPUVl69zsuTTgD+WVQTuusTiw== X-Received: by 2002:aa7:cd18:0:b0:41d:8df8:86e5 with SMTP id b24-20020aa7cd18000000b0041d8df886e5mr1080637edw.248.1650058638963; Fri, 15 Apr 2022 14:37:18 -0700 (PDT) Received: from mail-ed1-f43.google.com (mail-ed1-f43.google.com. [209.85.208.43]) by smtp.gmail.com with ESMTPSA id w14-20020a170906d20e00b006cee22553f7sm2029854ejz.213.2022.04.15.14.37.18 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 Apr 2022 14:37:18 -0700 (PDT) Received: by mail-ed1-f43.google.com with SMTP id c64so11119055edf.11 for ; Fri, 15 Apr 2022 14:37:18 -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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220415_143720_774574_AD2B4F4B X-CRM114-Status: GOOD ( 12.72 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel