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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDFDEC433F5 for ; Fri, 15 Apr 2022 23:32:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356569AbiDOXer (ORCPT ); Fri, 15 Apr 2022 19:34:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35280 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356578AbiDOXem (ORCPT ); Fri, 15 Apr 2022 19:34:42 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63DA07246D; Fri, 15 Apr 2022 16:32:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Maymh2MrV1jISeToWbYmaZRo07zKhpb63QtPmZTv7xg=; b=e6NCa/1p/FL935pR/uKS7VVL9i NxQnlxKWSJ+Ta17K4gYFWJzNJxaihd8RTbIG62Xl/cDePuFPsB30gWB0IcujU2gd2gfIoljv8kQWO a4vkc0OuVSydPevgNNt6rL2VgEbG29LDZ1FfJZ57cwqVmS5EKHamBYm8UIT3i5D8R9KlKtcVG+ble STvluOBWwYBbjHwrFiqkAnABEhloL7s/LtsDqOchuG+G1mM7EccYDiMhrFJe8oDuHSMfsmaQ8X2ZO ulDAhPZJC0uuEEiyM3RkXZI1CV+mIrNhruJHvBcWrbnL/74JsnfYmPNwQUGQEobNYpz1o7MRUgG+O UT4DzE+g==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nfVP8-00Gbuq-8e; Fri, 15 Apr 2022 23:31:06 +0000 Date: Sat, 16 Apr 2022 00:31:06 +0100 From: Matthew Wilcox To: Jesse Barnes Cc: Linus Torvalds , Yu Zhao , Andrew Morton , Justin Forbes , Stephen Rothwell , Linux-MM , Andi Kleen , Aneesh Kumar , Barry Song <21cnbao@gmail.com>, Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Johannes Weiner , Jonathan Corbet , 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 , Holger =?iso-8859-1?Q?Hoffst=E4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain Subject: Re: [page-reclaim] Re: [PATCH v10 08/14] mm: multi-gen LRU: support page table walks Message-ID: References: <20220414185654.e7150bcbe859e0dd4b9c61af@linux-foundation.org> <20220415121521.764a88dda55ae8c676ad26b0@linux-foundation.org> <20220415143220.cc37b0b0a368ed2bf2a821f8@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 15, 2022 at 04:24:14PM -0700, Jesse Barnes wrote: > On Fri, Apr 15, 2022 at 4:04 PM Linus Torvalds > wrote: > > And for ordinary users, a WARN_ON_ONCE() is about a million times > > better, becasue: > > > > - the machine will hopefully continue working, so they can report the warning > > > > - even when they don't notice them, distros tend to have automated > > reporting infrastructure > > > > That's why I absolutely *DETEST* those stupid BUG_ON() cases - they > > will often kill the machine with nasty locks held, resulting in a > > completely undebuggable thing that never gets reported. > > > > Yes, you can be careful and only put BUG_ON() in places where recovery > > is possible. But even then, they have no actual _advantages_ over just > > a WARN_ON_ONCE. > > Generally agreed, and not to belabor this relatively small issue, but in some > environments like cloud or managed client deployments, a crash can actually > be preferable so we can get a dump, reboot the machine, and get things going > again for the application or user, then debug offline. So having the > flexibility to > do that in those situations is helpful. And there, a full crash dump is better > than just a log report with the WARN info, since debugging may be easier with > all the kernel memory. But for those situations, don't you set panic_on_warn anyway? 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 D6B0AC433F5 for ; Fri, 15 Apr 2022 23:32:25 +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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=79V6pSLOvRP7BxGRDtp78co6qaiMHaNj0oS90sTN1NY=; b=m3j809YVGPXMb2 mN4V2GY1oZR6Mxg+O4ht2PrvEpHu52cyuojCR9s7Y1KjNgv9XUnAFcbWrf/R+qUcRIytD/wHRPT7l VQzvMfHLmGE7mQ2At2RHBtWQxHUHcNfV4GXFluMJ8XY2ryaT2/XbY8vGOmcF1yw9LszJLFPtPg2e6 W9/RjEQnqxhFbF7Wd9jjGiT+Yo4P/ikwYXZncn8pbygj7+TuWfWLJagkHTMsOO8deOhebw02MOn0M sUYekyqleasHWifGj6KYew1y0Q7TtRTJUS01IreXbR4hYMwnTYyxiFP+9qQir4cjNsq9k9uzDN8cB A3DdtpgYQOPQ6vcoy/pQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nfVPM-00BhGr-OD; Fri, 15 Apr 2022 23:31:20 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nfVPL-00BhGh-Ke for linux-arm-kernel@bombadil.infradead.org; Fri, 15 Apr 2022 23:31:19 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Maymh2MrV1jISeToWbYmaZRo07zKhpb63QtPmZTv7xg=; b=e6NCa/1p/FL935pR/uKS7VVL9i NxQnlxKWSJ+Ta17K4gYFWJzNJxaihd8RTbIG62Xl/cDePuFPsB30gWB0IcujU2gd2gfIoljv8kQWO a4vkc0OuVSydPevgNNt6rL2VgEbG29LDZ1FfJZ57cwqVmS5EKHamBYm8UIT3i5D8R9KlKtcVG+ble STvluOBWwYBbjHwrFiqkAnABEhloL7s/LtsDqOchuG+G1mM7EccYDiMhrFJe8oDuHSMfsmaQ8X2ZO ulDAhPZJC0uuEEiyM3RkXZI1CV+mIrNhruJHvBcWrbnL/74JsnfYmPNwQUGQEobNYpz1o7MRUgG+O UT4DzE+g==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nfVP8-00Gbuq-8e; Fri, 15 Apr 2022 23:31:06 +0000 Date: Sat, 16 Apr 2022 00:31:06 +0100 From: Matthew Wilcox To: Jesse Barnes Cc: Linus Torvalds , Yu Zhao , Andrew Morton , Justin Forbes , Stephen Rothwell , Linux-MM , Andi Kleen , Aneesh Kumar , Barry Song <21cnbao@gmail.com>, Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Johannes Weiner , Jonathan Corbet , 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 , Holger =?iso-8859-1?Q?Hoffst=E4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain Subject: Re: [page-reclaim] Re: [PATCH v10 08/14] mm: multi-gen LRU: support page table walks Message-ID: References: <20220414185654.e7150bcbe859e0dd4b9c61af@linux-foundation.org> <20220415121521.764a88dda55ae8c676ad26b0@linux-foundation.org> <20220415143220.cc37b0b0a368ed2bf2a821f8@linux-foundation.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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 04:24:14PM -0700, Jesse Barnes wrote: > On Fri, Apr 15, 2022 at 4:04 PM Linus Torvalds > wrote: > > And for ordinary users, a WARN_ON_ONCE() is about a million times > > better, becasue: > > > > - the machine will hopefully continue working, so they can report the warning > > > > - even when they don't notice them, distros tend to have automated > > reporting infrastructure > > > > That's why I absolutely *DETEST* those stupid BUG_ON() cases - they > > will often kill the machine with nasty locks held, resulting in a > > completely undebuggable thing that never gets reported. > > > > Yes, you can be careful and only put BUG_ON() in places where recovery > > is possible. But even then, they have no actual _advantages_ over just > > a WARN_ON_ONCE. > > Generally agreed, and not to belabor this relatively small issue, but in some > environments like cloud or managed client deployments, a crash can actually > be preferable so we can get a dump, reboot the machine, and get things going > again for the application or user, then debug offline. So having the > flexibility to > do that in those situations is helpful. And there, a full crash dump is better > than just a log report with the WARN info, since debugging may be easier with > all the kernel memory. But for those situations, don't you set panic_on_warn anyway? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel