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, URIBL_BLOCKED,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 158A8C2D0A7 for ; Tue, 8 Sep 2020 20:14:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C58EA208FE for ; Tue, 8 Sep 2020 20:14:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=cisco.com header.i=@cisco.com header.b="jCZK8OZ6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730859AbgIHUOi (ORCPT ); Tue, 8 Sep 2020 16:14:38 -0400 Received: from rcdn-iport-9.cisco.com ([173.37.86.80]:59051 "EHLO rcdn-iport-9.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730634AbgIHUOd (ORCPT ); Tue, 8 Sep 2020 16:14:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=1785; q=dns/txt; s=iport; t=1599596072; x=1600805672; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=T8mkCE6PfAz3UDsDi/PeT6rnbi3jy36h40OMXp16Ecg=; b=jCZK8OZ67a1lYCRulutuBlJ13wtVq7igOdRqKQokHP+OckMclQuQ58KZ wPCavBuUZa0qw1h1O+GliN6ZWXTX+7OfFwavQxMw3TVuj1rcSfgVuwmBn vklexWsVe6KNiXdYSJFGHv8wOkLt8MmTCqYwjamimMfO62drJJwpiarg9 8=; X-IronPort-AV: E=Sophos;i="5.76,406,1592870400"; d="scan'208";a="732193483" Received: from rcdn-core-4.cisco.com ([173.37.93.155]) by rcdn-iport-9.cisco.com with ESMTP/TLS/DHE-RSA-SEED-SHA; 08 Sep 2020 20:14:30 +0000 Received: from sjc-ads-9087.cisco.com (sjc-ads-9087.cisco.com [10.30.208.97]) by rcdn-core-4.cisco.com (8.15.2/8.15.2) with ESMTP id 088KETHu020960; Tue, 8 Sep 2020 20:14:30 GMT Received: by sjc-ads-9087.cisco.com (Postfix, from userid 396877) id BDD7AA40; Tue, 8 Sep 2020 13:14:29 -0700 (PDT) From: Julius Hemanth Pitti To: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, guro@fb.com Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, xe-linux-external@cisco.com, Julius Hemanth Pitti Subject: [PATCH v2] mm: memcg: yield cpu when we fail to charge pages Date: Tue, 8 Sep 2020 13:14:26 -0700 Message-Id: <20200908201426.14837-1-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-4.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 Acked-by: Roman Gushchin --- Changes in v2: - Added comments. - Added "Acked-by: Roman Gushchin ". --- mm/memcontrol.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index cfa6cbad21d5..4f293bf8c7ed 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2745,6 +2745,15 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, if (fatal_signal_pending(current)) goto force; + /* + * We failed to charge even after retries, give oom_reaper or + * other process a change to make some free pages. + * + * On non-preemptive, Non-SMP system, this is critical, else + * we keep retrying with no success, forever. + */ + 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