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 05B62C433EF for ; Fri, 15 Apr 2022 23:37:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230442AbiDOXkC (ORCPT ); Fri, 15 Apr 2022 19:40:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47538 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234247AbiDOXkA (ORCPT ); Fri, 15 Apr 2022 19:40:00 -0400 Received: from mail-yw1-x1131.google.com (mail-yw1-x1131.google.com [IPv6:2607:f8b0:4864:20::1131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2C5281673 for ; Fri, 15 Apr 2022 16:37:30 -0700 (PDT) Received: by mail-yw1-x1131.google.com with SMTP id 00721157ae682-2ef4a241cc5so88545677b3.2 for ; Fri, 15 Apr 2022 16:37:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=GBzN0oGFUFjzpywBXSVux/Xmu/oJE1kMpJ05D3WkT7w=; b=gEXUAF2gs2CTa7hRCFDB89694XtziZL6aHbaBs2Oxd80FnFUNaJ+CyTYohPLbzMFEz kiEZ4GY9F4nR/3mlIWDrB5YBrtZjed+jnmGf+30p6GhxDwTopugU11f5HXvKaTGwrMBj eb1NkZHXjKoHBYKfyIXTvWnbAcgX8s5qXY1I/41fh4CsWhvwLr1N83/2Gub1q+i2cmDL NehpdNnityZBdgPXErbsuVGsbZ8XFXb/GDHBWB13ZjkKX4nVOz7eHLObkPqRKMqXUtzx IeEEfQw3BfIQBxVoiKFwkCi/4AspSYsixdMVKxrJxxeHKv02PgAJH6ZZzu+kUUAzsydS QpFQ== 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=GBzN0oGFUFjzpywBXSVux/Xmu/oJE1kMpJ05D3WkT7w=; b=4tAN/NIO3gO2CZR03tEV1MQPut9RDxxXeRI7HQRgNGTjb9XEeLC9wtqqaKjgIJL9bM qWkV8+o42lZ35KxpMCT4XnaLBtjK3+1Mh1o92F+fBUzs2hrgy42w8MDlNG0KOiBnKSUR cyzVsTeI1wOj0BmaeFrHDtkeABvusgFuGh+ZuOpwkgGERxPn1t3S/imTqW/S8yU3LcoQ 5yNVCb8Az0dBZZ6w7J+vUDLXVZc9V6+D3BzZLEeHPpauV4i2E1/O0tN29axIGxggy9et fPcyqUQ6MzDa6UyP8AZN+j5ywe02Gb62n5zI51YLn1KoG5+DMTYMWGbO9zE0ecf8Og15 GRNQ== X-Gm-Message-State: AOAM533uUnct1vLwfEt/R7YjETSvnieIqiGALZVdncbKmaq+wm0Po5CW P2zb+2MmqFObxzoJJkrftwaxrqZP3UMTjy152POAqQ== X-Google-Smtp-Source: ABdhPJyg4K4LACqH2AcGFF1qsZf4zXwnYa7M+1ZR/KBW0Gvu89HiGnqnLTcYYAIN5JZCFsJgUKCChcvn9V71cx1qJ0Y= X-Received: by 2002:a81:8b47:0:b0:2e6:57ba:5f84 with SMTP id e7-20020a818b47000000b002e657ba5f84mr1217410ywk.285.1650065849882; Fri, 15 Apr 2022 16:37:29 -0700 (PDT) MIME-Version: 1.0 References: <20220414185654.e7150bcbe859e0dd4b9c61af@linux-foundation.org> <20220415121521.764a88dda55ae8c676ad26b0@linux-foundation.org> <20220415143220.cc37b0b0a368ed2bf2a821f8@linux-foundation.org> In-Reply-To: From: Jesse Barnes Date: Fri, 15 Apr 2022 16:37:17 -0700 Message-ID: Subject: Re: [page-reclaim] Re: [PATCH v10 08/14] mm: multi-gen LRU: support page table walks To: Matthew Wilcox 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 , =?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, 4:31 PM Matthew Wilcox wrote: > > 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? Yes ignore me. Jesse "returning to his cave of ignorace" Barnes 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 8B75AC433EF for ; Fri, 15 Apr 2022 23:38:39 +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=5jwdNKzdYdPLfL5+SN9KBxCWuDt2SdWQzSVoiWulegw=; b=3HGqmGK5xX64pf EjkccAU3fWlL9vuIqXmpc0kP1QPhUawKcI+g47HdWfCHf9iqVoKQ/Jk0mWbV1QSw3lW4Ko47EalAD FNHP21m0GlOc8xY276SRErSRSybErx3XBuXQaOn4Akz4AAx8UYIuBH52mlJro2j5NMxmFrWuiTrhR CWuCO6enELWAsswN2iBYZapLOx2PHO69+68PInQy08cEZ6j7xDKz1RTvR/v/GkVY4U4lZnkSocmjB FS2U8IpNmGWZRHwet4YM4pouF8ozETEGDSYby/qoyTNgxFggYZtOceueTbR5XVGgwSvNGcc4XwMWZ a4tz/ojUmEXEiz701ZDg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nfVVO-00BiLI-Mc; Fri, 15 Apr 2022 23:37:34 +0000 Received: from mail-yw1-x112d.google.com ([2607:f8b0:4864:20::112d]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nfVVL-00BiJ5-E2 for linux-arm-kernel@lists.infradead.org; Fri, 15 Apr 2022 23:37:33 +0000 Received: by mail-yw1-x112d.google.com with SMTP id 00721157ae682-2ebf4b91212so95383297b3.8 for ; Fri, 15 Apr 2022 16:37:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=GBzN0oGFUFjzpywBXSVux/Xmu/oJE1kMpJ05D3WkT7w=; b=gEXUAF2gs2CTa7hRCFDB89694XtziZL6aHbaBs2Oxd80FnFUNaJ+CyTYohPLbzMFEz kiEZ4GY9F4nR/3mlIWDrB5YBrtZjed+jnmGf+30p6GhxDwTopugU11f5HXvKaTGwrMBj eb1NkZHXjKoHBYKfyIXTvWnbAcgX8s5qXY1I/41fh4CsWhvwLr1N83/2Gub1q+i2cmDL NehpdNnityZBdgPXErbsuVGsbZ8XFXb/GDHBWB13ZjkKX4nVOz7eHLObkPqRKMqXUtzx IeEEfQw3BfIQBxVoiKFwkCi/4AspSYsixdMVKxrJxxeHKv02PgAJH6ZZzu+kUUAzsydS QpFQ== 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=GBzN0oGFUFjzpywBXSVux/Xmu/oJE1kMpJ05D3WkT7w=; b=SNlBA5mUj2RL5YmEtvVKpfaKeFDwO5x2hF5MlhvsX09752pGBUje9MaRRy7jKrBQjC w3w4p/oHpQbDY/vHiVK26goWa29ndmrPHbseMVcB5jAsFFD5xUkzH+oeYNGLK9b5kOJG kNU4TNj7fGRPItDD+DiyObd/Um6n1WfYoiPvJ3M8fcfliXYvrPhA0lUBgLbr0KVXVF0T sK7SafvnB6lCGdmANvIuV3JD4rH1NRNakl0kbduYMrBTUofmsiJXi4+QyGjk9PvnwEbs H9Sly+y2XD+KPzwpxCYFdz/GULQjix6aWyMwd1SolR2QOhlM302QR9hUXF2YfqDD/iAr 0ckw== X-Gm-Message-State: AOAM531JFDPVcrDOEiVIossWBEcp7rsXsemn1vm5O2N2BK0a+iG68KEu xTu/qR5JnkBqSrTlLinb0A6DBKu0+NMGzIEcMKkKpg== X-Google-Smtp-Source: ABdhPJyg4K4LACqH2AcGFF1qsZf4zXwnYa7M+1ZR/KBW0Gvu89HiGnqnLTcYYAIN5JZCFsJgUKCChcvn9V71cx1qJ0Y= X-Received: by 2002:a81:8b47:0:b0:2e6:57ba:5f84 with SMTP id e7-20020a818b47000000b002e657ba5f84mr1217410ywk.285.1650065849882; Fri, 15 Apr 2022 16:37:29 -0700 (PDT) MIME-Version: 1.0 References: <20220414185654.e7150bcbe859e0dd4b9c61af@linux-foundation.org> <20220415121521.764a88dda55ae8c676ad26b0@linux-foundation.org> <20220415143220.cc37b0b0a368ed2bf2a821f8@linux-foundation.org> In-Reply-To: From: Jesse Barnes Date: Fri, 15 Apr 2022 16:37:17 -0700 Message-ID: Subject: Re: [page-reclaim] Re: [PATCH v10 08/14] mm: multi-gen LRU: support page table walks To: Matthew Wilcox 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 , =?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_163731_515449_355D7092 X-CRM114-Status: GOOD ( 25.61 ) 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, 4:31 PM Matthew Wilcox wrote: > > 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? Yes ignore me. Jesse "returning to his cave of ignorace" Barnes _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel