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=-12.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1, 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 96DBEC2BAEE for ; Wed, 11 Mar 2020 19:38:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8600420749 for ; Wed, 11 Mar 2020 19:38:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="gEjOycvx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731085AbgCKTiL (ORCPT ); Wed, 11 Mar 2020 15:38:11 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:40746 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730925AbgCKTiK (ORCPT ); Wed, 11 Mar 2020 15:38:10 -0400 Received: by mail-pg1-f194.google.com with SMTP id t24so1738740pgj.7 for ; Wed, 11 Mar 2020 12:38:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=Zb5q/Mu4Y05A8mwi2SFVQb8nWna0MTPdNN6cb7H8VpE=; b=gEjOycvx4YQW2uEn6K7qwHEwfNAGZYNaSKbDvy1IVY56seaG5DAmfh9kBhmrYGMXqs ZqlKVr1XsUWCWptcndhsmwO+Mtiq+tcdxEPjddRld13v5IEbCsKSLYc3mqVr/LB9UbYs zboqVnO8hTlArH7Wi/Z0HcqJP/jrr5og7GZYWIP5h64jIuXT5+E+j66XWTvNUP1/kiLD OC/jyASsnhZOhK4+g4oHDSRhZYjk9f7n9t1ZTyLlA1Og3ObGHHgXxcfjPOPJo1pyeX4K NJzwpMsOguK2wm7Z1Xgr8sqdJSnMYtAK3lVEKy3JGL3JELhaYj4cihBUmV6I1EWIAUcP sNsg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version; bh=Zb5q/Mu4Y05A8mwi2SFVQb8nWna0MTPdNN6cb7H8VpE=; b=V4LXdfkBRM8qHTiQSBlMdWmZ7SN5EJiUwHQNsayFUCjOMe6POUQAtaPu2dYxUiWG8z oB+FBoLCN9uovF9ASrzmwLSyOk1x8ZLqsRzvJwKshT25FWSyjX51XBvpfRH8ZPbnZfrE JERNMD5+fvDnuWbSnqTUXLNbJIoNOigblGSU69KvKfvj8VnxyShJ3QwqMdkRzrzxfUO2 YlPRmSHrJuU6TnsWO2HfaK16j+HQ/EqIDhodDxLiVhlGxzGXWVQYNILZhW1NlfPo5pWU 8oU5+pt8aGLxnmJ6nf2pYI+BghpaMlH9cHT5NBW8BRojZlvasYcnFRd8zQRRS3bg+yph F0og== X-Gm-Message-State: ANhLgQ1V+TNhYN1X+BTQNJdLQbKxUAfG1yb3GVEHAUapTzJikdvWnr+b zczlxxzCnn5h6tPGvgIvxfC+9Q== X-Google-Smtp-Source: ADFU+vu4w2Fjd9qLpxvfjtML0AhQNSJS4jd+sFLDO6cpsSiLPD5qfQgTvXBo2xt9ibO4JgPeFVVIxg== X-Received: by 2002:a62:5cc1:: with SMTP id q184mr2272743pfb.259.1583955489598; Wed, 11 Mar 2020 12:38:09 -0700 (PDT) Received: from [2620:15c:17:3:3a5:23a7:5e32:4598] ([2620:15c:17:3:3a5:23a7:5e32:4598]) by smtp.gmail.com with ESMTPSA id x72sm13897760pfc.156.2020.03.11.12.38.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Mar 2020 12:38:08 -0700 (PDT) Date: Wed, 11 Mar 2020 12:38:07 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Tetsuo Handa cc: Andrew Morton , Vlastimil Babka , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [patch] mm, oom: prevent soft lockup on memcg oom for UP systems In-Reply-To: <7a6170fc-b247-e327-321a-b99fb53f552d@i-love.sakura.ne.jp> Message-ID: References: <0e5ca6ee-d460-db8e-aba2-79aa7a66fad1@I-love.SAKURA.ne.jp> <7a6170fc-b247-e327-321a-b99fb53f552d@i-love.sakura.ne.jp> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 11 Mar 2020, Tetsuo Handa wrote: > >>> diff --git a/mm/vmscan.c b/mm/vmscan.c > >>> --- a/mm/vmscan.c > >>> +++ b/mm/vmscan.c > >>> @@ -2637,6 +2637,8 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) > >>> unsigned long reclaimed; > >>> unsigned long scanned; > >>> > >>> + cond_resched(); > >>> + > >> > >> Is this safe for CONFIG_PREEMPTION case? If current thread has realtime priority, > >> can we guarantee that the OOM victim (well, the OOM reaper kernel thread rather > >> than the OOM victim ?) gets scheduled? > >> > > > > I think it's the best we can do that immediately solves the issue unless > > you have another idea in mind? > > "schedule_timeout_killable(1) outside of oom_lock" or "the OOM reaper grabs oom_lock > so that allocating threads guarantee that the OOM reaper gets scheduled" or "direct OOM > reaping so that allocating threads guarantee that some memory is reclaimed". > The cond_resched() here is needed if the iteration is lengthy depending on the number of descendant memcgs already. schedule_timeout_killable(1) does not make any guarantees that current will be scheduled after the victim or oom_reaper on UP systems. If you have an alternate patch to try, we can test it. But since this cond_resched() is needed anyway, I'm not sure it will change the result. > > > >>> switch (mem_cgroup_protected(target_memcg, memcg)) { > >>> case MEMCG_PROT_MIN: > >>> /* > >>> > >> > >