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=-20.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham 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 9EB12C43461 for ; Tue, 8 Sep 2020 18:59:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4DDF32068D for ; Tue, 8 Sep 2020 18:59:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=cisco.com header.i=@cisco.com header.b="KnYh3lHP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731426AbgIHS7B (ORCPT ); Tue, 8 Sep 2020 14:59:01 -0400 Received: from rcdn-iport-9.cisco.com ([173.37.86.80]:22168 "EHLO rcdn-iport-9.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730572AbgIHS6w (ORCPT ); Tue, 8 Sep 2020 14:58:52 -0400 X-Greylist: delayed 428 seconds by postgrey-1.27 at vger.kernel.org; Tue, 08 Sep 2020 14:58:51 EDT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=1391; q=dns/txt; s=iport; t=1599591531; x=1600801131; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=m2WVpZpXrtQFXh3Ql4JrliPwX+fM66/2SHqLhNxgwkY=; b=KnYh3lHP4/Pu4OSlhFDHLVbfoxOVsRcMaYRNRv459un7R/dOKJu/TVfZ knVJe3j1CGYS+0nTi6yI2AAbBjKCaDRKp537mXeHkDVYbh9mHX4Esi4E0 spzQSsk0yz4pU8CBK7o05+KtEyqKAqKdiHtDVeOhk+uBaODMXfKpMSj26 Y=; X-IronPort-AV: E=Sophos;i="5.76,406,1592870400"; d="scan'208";a="732158731" Received: from rcdn-core-1.cisco.com ([173.37.93.152]) by rcdn-iport-9.cisco.com with ESMTP/TLS/DHE-RSA-SEED-SHA; 08 Sep 2020 18:51:43 +0000 Received: from sjc-ads-9087.cisco.com (sjc-ads-9087.cisco.com [10.30.208.97]) by rcdn-core-1.cisco.com (8.15.2/8.15.2) with ESMTP id 088IphYE005304; Tue, 8 Sep 2020 18:51:43 GMT Received: by sjc-ads-9087.cisco.com (Postfix, from userid 396877) id D89BFBFD; Tue, 8 Sep 2020 11:51:42 -0700 (PDT) From: Julius Hemanth Pitti To: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, xe-linux-external@cisco.com, Julius Hemanth Pitti Subject: [PATCH] mm: memcg: yield cpu when we fail to charge pages Date: Tue, 8 Sep 2020 11:50:51 -0700 Message-Id: <20200908185051.62420-1-jpitti@cisco.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Auto-Response-Suppress: DR, OOF, AutoReply X-Outbound-SMTP-Client: 10.30.208.97, sjc-ads-9087.cisco.com X-Outbound-Node: rcdn-core-1.cisco.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For non root CG, in try_charge(), we keep trying to charge until we succeed. On non-preemptive kernel, when we are OOM, this results in holding CPU forever. On SMP systems, this doesn't create a big problem because oom_reaper get a change to kill victim and make some free pages. However on a single-core CPU (or cases where oom_reaper pinned to same CPU where try_charge is executing), oom_reaper shall never get scheduled and we stay in try_charge forever. Steps to repo this on non-smp: 1. mount -t tmpfs none /sys/fs/cgroup 2. mkdir /sys/fs/cgroup/memory 3. mount -t cgroup none /sys/fs/cgroup/memory -o memory 4. mkdir /sys/fs/cgroup/memory/0 5. echo 40M > /sys/fs/cgroup/memory/0/memory.limit_in_bytes 6. echo $$ > /sys/fs/cgroup/memory/0/tasks 7. stress -m 5 --vm-bytes 10M --vm-hang 0 Signed-off-by: Julius Hemanth Pitti --- mm/memcontrol.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 0d6f3ea86738..4620d70267cb 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2652,6 +2652,8 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, if (fatal_signal_pending(current)) goto force; + cond_resched(); + /* * keep retrying as long as the memcg oom killer is able to make * a forward progress or bypass the charge if the oom killer -- 2.17.1