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=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 D6577C433EF for ; Wed, 22 Sep 2021 06:18:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BBF9460F12 for ; Wed, 22 Sep 2021 06:18:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232688AbhIVGUB (ORCPT ); Wed, 22 Sep 2021 02:20:01 -0400 Received: from relay.sw.ru ([185.231.240.75]:43430 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232627AbhIVGT5 (ORCPT ); Wed, 22 Sep 2021 02:19:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:From: Subject; bh=kKOaxfW8XB27athhg5MSO4zSrJCF13FJZud0x020yE8=; b=IHdKcPfUPcD6gzlte oJgaZ+oyFAcfYtjMjvklvMzm5jQS4DtCDM0LlYM5w9D6naqxNoSSahSKPvMVS4juqoA91FoVEkznB cDzBYB6U1kH2Qdy2Jm6UnAKEWVom8SxyCBNxI9wF++kxzdIFPCmmAxZTZY1o/Fj6aFsZSciLhCYL0 =; Received: from [10.93.0.56] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mSvaI-002n84-BQ; Wed, 22 Sep 2021 09:18:22 +0300 Subject: Re: [PATCH mm] vmalloc: back off when the current task is OOM-killed To: Andrew Morton Cc: Tetsuo Handa , Michal Hocko , Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel@openvz.org, "Uladzislau Rezki (Sony)" References: <20210919163126.431674722b8db218453dc18c@linux-foundation.org> <20210921115523.8606cea0b2f0a5ca4e79cbd0@linux-foundation.org> From: Vasily Averin Message-ID: <9eb3d50d-9777-087d-eee8-36573f32cf14@virtuozzo.com> Date: Wed, 22 Sep 2021 09:18:21 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210921115523.8606cea0b2f0a5ca4e79cbd0@linux-foundation.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/21/21 9:55 PM, Andrew Morton wrote: > On Mon, 20 Sep 2021 13:59:35 +0300 Vasily Averin wrote: > >> On 9/20/21 4:22 AM, Tetsuo Handa wrote: >>> On 2021/09/20 8:31, Andrew Morton wrote: >>>> On Fri, 17 Sep 2021 11:06:49 +0300 Vasily Averin wrote: >>>> >>>>> Huge vmalloc allocation on heavy loaded node can lead to a global >>>>> memory shortage. A task called vmalloc can have the worst badness >>>>> and be chosen by OOM-killer, however received fatal signal and >>>>> oom victim mark does not interrupt allocation cycle. Vmalloc will >>>>> continue allocating pages over and over again, exacerbating the crisis >>>>> and consuming the memory freed up by another killed tasks. >>>>> >>>>> This patch allows OOM-killer to break vmalloc cycle, makes OOM more >>>>> effective and avoid host panic. >>>>> >>>>> Unfortunately it is not 100% safe. Previous attempt to break vmalloc >>>>> cycle was reverted by commit b8c8a338f75e ("Revert "vmalloc: back off when >>>>> the current task is killed"") due to some vmalloc callers did not handled >>>>> failures properly. Found issues was resolved, however, there may >>>>> be other similar places. >>>> >>>> Well that was lame of us. >>>> >>>> I believe that at least one of the kernel testbots can utilize fault >>>> injection. If we were to wire up vmalloc (as we have done with slab >>>> and pagealloc) then this will help to locate such buggy vmalloc callers. >> >> Andrew, could you please clarify how we can do it? >> Do you mean we can use exsiting allocation fault injection infrastructure to trigger >> such kind of issues? Unfortunately I found no ways to reach this goal. >> It allows to emulate single faults with small probability, however it is not enough, >> we need to completely disable all vmalloc allocations. > > I don't see why there's a problem? You're saying "there might still be > vmalloc() callers which don't correctly handle allocation failures", > yes? > > I'm suggesting that we use fault injection to cause a small proportion > of vmalloc() calls to artificially fail, so such buggy callers will > eventually be found and fixed. Why does such a scheme require that > *all* vmalloc() calls fail? Let me explain. 1) it is not trivial to use current allocation fault injection to cause a small proportion of vmalloc() calls to artificially fail. vmalloc __vmalloc_node __vmalloc_node_range __vmalloc_area_node vm_area_alloc_pages vm_area_alloc_pages uses new __alloc_pages_bulk subsystem, requesting up to 100 pages in cycle. __alloc_pages_bulk() can be interrupted by allocation fault injection, however in this case vm_area_alloc_pages() will failback to old-style page allocation cycle. In general case it successfully finishes allocation and vmalloc itself will not fail. To fail vmalloc we need to fail both alloc_pages_bulk_array_node() and alloc_pages_node() together. 2) if we failed single vmalloc it is not enough. I would remind, we want to emulate fatal signal reaction. However I afraid dying task can execute a quite complex rollback procedure. This rollback can call another vmalloc and last one will be failed again on fatal_signal_pending check. To emulate this behavior in fault injection we need to disable all following vmalloc calls of our victim, pseudo-"dying" task. I doubt both these goals can be reached by current allocation fault injection subsystem, I do not understand how to configure it accordingly. Thank you, Vasily Averin