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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5986C433B4 for ; Thu, 20 May 2021 12:41:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C87B4613BA for ; Thu, 20 May 2021 12:41:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241206AbhETMmU (ORCPT ); Thu, 20 May 2021 08:42:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241955AbhETMlZ (ORCPT ); Thu, 20 May 2021 08:41:25 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 21210C0611EA for ; Thu, 20 May 2021 05:00:53 -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=r9GR7msVdIEp3a4rq9cpsOCHYoC70zlaenAZiGtT+tk=; b=KLQf3eixwTu2GrcJ/dqnzHwq49 t22XDmAw5cxkLn18JPDoYk/HBuxipOHK5s66zUsynb/kBtDog3sAkeuEkmiiNEt1KGG9g0Bhk70Q+ 7oUmoIallZ7meR5UoBvyABv7aQJO/kEYvpt+LO9oYQQgvwQFLZlcj6yCjNR0trsDFesHE7bVK9jag AQX+e96f+xuS0nKsrNG1Ol3JefZL01uq/wYnGYr/yAY6gLNT0YkhpBOl6jl872GovxfGk67/GKwnN 6d2VH9unjF6QnxJcTVbMn9cx/m4NBkXIRhAekHL3Z7M1pzeb7CW2prMKHGc34xdBb6Q2XrX5j0A2W NeaYucSg==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1ljhHw-00FwX2-4q; Thu, 20 May 2021 11:57:11 +0000 Date: Thu, 20 May 2021 12:56:28 +0100 From: Matthew Wilcox To: Aaron Tomlin Cc: Vlastimil Babka , Andrew Morton , linux-mm@kvack.org, mhocko@suse.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm/page_alloc: bail out on fatal signal during reclaim/compaction retry attempt Message-ID: References: <20210519201743.3260890-1-atomlin@redhat.com> <20210519213455.97ff95f0124b4120787f8314@linux-foundation.org> <9b11dcd8-bc3b-aae9-feb1-43543bf9e22f@suse.cz> <20210520114257.huqhkqsdrhohn3u5@ava.usersys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210520114257.huqhkqsdrhohn3u5@ava.usersys.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 20, 2021 at 12:42:57PM +0100, Aaron Tomlin wrote: > On Thu 2021-05-20 12:20 +0200, Vlastimil Babka wrote: > > On 5/20/21 6:34 AM, Andrew Morton wrote: > > > > > > What observed problems motivated this change? > > > > > > What were the observed runtime effects of this change? > > > > Yep those details from the previous thread should be included here. > > Fair enough. > > During kernel crash dump/or vmcore analysis: I discovered in the context of > __alloc_pages_slowpath() the value stored in the no_progress_loops variable > was found to be 31,611,688 i.e. well above MAX_RECLAIM_RETRIES; and a fatal > signal was pending against current. While this is true, it's not really answering Andrew's question. What we want as part of the commit message is something like: "A customer experienced a low memory situation and sent their task a fatal signal. Instead of dying promptly, it looped in the page allocator failing to make progress because ..." > > #6 [ffff00002e78f7c0] do_try_to_free_pages+0xe4 at ffff00001028bd24 > #7 [ffff00002e78f840] try_to_free_pages+0xe4 at ffff00001028c0f4 > #8 [ffff00002e78f900] __alloc_pages_nodemask+0x500 at ffff0000102cd130 > > // w28 = *(sp + 148) /* no_progress_loops */ > 0xffff0000102cd1e0 <__alloc_pages_nodemask+0x5b0>: ldr w0, [sp,#148] > // w0 = w0 + 0x1 > 0xffff0000102cd1e4 <__alloc_pages_nodemask+0x5b4>: add w0, w0, #0x1 > // *(sp + 148) = w0 > 0xffff0000102cd1e8 <__alloc_pages_nodemask+0x5b8>: str w0, [sp,#148] > // if (w0 >= 0x10) > // goto __alloc_pages_nodemask+0x904 > 0xffff0000102cd1ec <__alloc_pages_nodemask+0x5bc>: cmp w0, #0x10 > 0xffff0000102cd1f0 <__alloc_pages_nodemask+0x5c0>: b.gt 0xffff0000102cd534 > > - The stack pointer was 0xffff00002e78f900 > > crash> p *(int *)(0xffff00002e78f900+148) > $1 = 31611688 > > crash> ps 521171 > PID PPID CPU TASK ST %MEM VSZ RSS COMM > > 521171 1 36 ffff8080e2128800 RU 0.0 34789440 18624 special > > crash> p &((struct task_struct *)0xffff8080e2128800)->signal.shared_pending > $2 = (struct sigpending *) 0xffff80809a416e40 > > crash> p ((struct sigpending *)0xffff80809a416e40)->signal.sig[0] > $3 = 0x804100 > > crash> sig -s 0x804100 > SIGKILL SIGTERM SIGXCPU > > crash> p ((struct sigpending *)0xffff80809a416e40)->signal.sig[0] & 1U << (9 - 1) > $4 = 0x100 > > > Unfortunately, this incident was not reproduced, to date. > > > > > > Kind regards, > > -- > Aaron Tomlin