From patchwork Sat Oct 23 13:20:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vasily Averin X-Patchwork-Id: 12579615 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35044C433EF for ; Sat, 23 Oct 2021 13:20:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9F4926101B for ; Sat, 23 Oct 2021 13:20:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9F4926101B Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=virtuozzo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 39264940008; Sat, 23 Oct 2021 09:20:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3417E940007; Sat, 23 Oct 2021 09:20:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 23102940008; Sat, 23 Oct 2021 09:20:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0154.hostedemail.com [216.40.44.154]) by kanga.kvack.org (Postfix) with ESMTP id 17241940007 for ; Sat, 23 Oct 2021 09:20:44 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id B6A75181B04A7 for ; Sat, 23 Oct 2021 13:20:43 +0000 (UTC) X-FDA: 78727761966.15.CDBE69E Received: from relay.sw.ru (relay.sw.ru [185.231.240.75]) by imf17.hostedemail.com (Postfix) with ESMTP id 52E37F00039C for ; Sat, 23 Oct 2021 13:20:43 +0000 (UTC) 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:Subject :From; bh=AxIxgS5Zgx5Dv7xkNVoOHoVf+L4ocZrzhwvz5mTzh88=; b=cQNq11A5aFx4UAhxGGN cnAAMC/aSb0yZ3qBaxFUMcr36XaP+aXXQVY+4ZrC5LYCfug4p/scKAzhXlvBqhNF2l6MH3rxAlDbE xvXLaZIm4Gh3SWpdeWYZ2bk7dWFJbCHs/E5S6zFqn2Op0BcpzQlGU8Fbk+FidqIkfcEnjry/OcI=; Received: from [172.29.1.17] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1meGwx-006vQz-Ux; Sat, 23 Oct 2021 16:20:40 +0300 From: Vasily Averin Subject: [PATCH memcg v3 2/3] mm, oom: do not trigger out_of_memory from the #PF To: Michal Hocko , Johannes Weiner , Vladimir Davydov , Andrew Morton Cc: Roman Gushchin , Uladzislau Rezki , Vlastimil Babka , Shakeel Butt , Mel Gorman , Tetsuo Handa , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel@openvz.org References: Message-ID: Date: Sat, 23 Oct 2021 16:20:18 +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: Content-Language: en-US X-Stat-Signature: a7gwk9d5hefg114mm5nzhkcytau885qn Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=virtuozzo.com header.s=relay header.b=cQNq11A5; spf=pass (imf17.hostedemail.com: domain of vvs@virtuozzo.com designates 185.231.240.75 as permitted sender) smtp.mailfrom=vvs@virtuozzo.com; dmarc=pass (policy=quarantine) header.from=virtuozzo.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 52E37F00039C X-HE-Tag: 1634995243-770728 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Michal Hocko Any allocation failure during the #PF path will return with VM_FAULT_OOM which in turn results in pagefault_out_of_memory. This can happen for 2 different reasons. a) Memcg is out of memory and we rely on mem_cgroup_oom_synchronize to perform the memcg OOM handling or b) normal allocation fails. The later is quite problematic because allocation paths already trigger out_of_memory and the page allocator tries really hard to not fail allocations. Anyway, if the OOM killer has been already invoked there is no reason to invoke it again from the #PF path. Especially when the OOM condition might be gone by that time and we have no way to find out other than allocate. Moreover if the allocation failed and the OOM killer hasn't been invoked then we are unlikely to do the right thing from the #PF context because we have already lost the allocation context and restictions and therefore might oom kill a task from a different NUMA domain. This all suggests that there is no legitimate reason to trigger out_of_memory from pagefault_out_of_memory so drop it. Just to be sure that no #PF path returns with VM_FAULT_OOM without allocation print a warning that this is happening before we restart the #PF. [VvS: #PF allocation can hit into limit of cgroup v1 kmem controller. This is a local problem related to memcg, however, it causes unnecessary global OOM kills that are repeated over and over again and escalate into a real disaster. This has been broken since kmem accounting has been introduced for cgroup v1 (3.8). There was no kmem specific reclaim for the separate limit so the only way to handle kmem hard limit was to return with ENOMEM. In upstream the problem will be fixed by removing the outdated kmem limit, however stable and LTS kernels cannot do it and are still affected. This patch fixes the problem and should be backported into stable/LTS.] Cc: stable@vger.kernel.org Signed-off-by: Michal Hocko Signed-off-by: Vasily Averin Acked-by: Michal Hocko --- v2: hook with fatal_signal_pending() has beem moved into a separate patch, improved patch description, removed "Fixed" mark. --- mm/oom_kill.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 1deef8c7a71b..f98954befafb 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -1120,19 +1120,15 @@ bool out_of_memory(struct oom_control *oc) } /* - * The pagefault handler calls here because it is out of memory, so kill a - * memory-hogging task. If oom_lock is held by somebody else, a parallel oom - * killing is already in progress so do nothing. + * The pagefault handler calls here because some allocation has failed. We have + * to take care of the memcg OOM here because this is the only safe context without + * any locks held but let the oom killer triggered from the allocation context care + * about the global OOM. */ void pagefault_out_of_memory(void) { - struct oom_control oc = { - .zonelist = NULL, - .nodemask = NULL, - .memcg = NULL, - .gfp_mask = 0, - .order = 0, - }; + static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL, + DEFAULT_RATELIMIT_BURST); if (mem_cgroup_oom_synchronize(true)) return; @@ -1140,10 +1136,8 @@ void pagefault_out_of_memory(void) if (fatal_signal_pending(current)) return; - if (!mutex_trylock(&oom_lock)) - return; - out_of_memory(&oc); - mutex_unlock(&oom_lock); + if (__ratelimit(&pfoom_rs)) + pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n"); } SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)