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=-10.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 8AFE5C43387 for ; Sun, 13 Jan 2019 17:36:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5E6D9206B6 for ; Sun, 13 Jan 2019 17:36:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547400968; bh=jjntsjE8ahNqP/UzM8oD8ff96MQ+9OyJzKUq6WIPBvk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=WJqjcWmgdt3XALe33xVIF0diTRU+JYKSW0TezVgpvsH1kjKrT6Z5KXFjHH6z7dlX0 xAe0hIEO5WqDrC5tqcezsNYYlE2OjPPUa6LOpBXjeeYVa1kIz8XiyJDvqqoh3arlo+ oP46aNVVK4tG4lj2yY+rmVbeoWHQs7bD7H4MkSao= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726788AbfAMRgH (ORCPT ); Sun, 13 Jan 2019 12:36:07 -0500 Received: from mx2.suse.de ([195.135.220.15]:54010 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726254AbfAMRgG (ORCPT ); Sun, 13 Jan 2019 12:36:06 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4D231AF00; Sun, 13 Jan 2019 17:36:04 +0000 (UTC) Date: Sun, 13 Jan 2019 18:36:03 +0100 From: Michal Hocko To: Tetsuo Handa Cc: Andrew Morton , linux-mm@kvack.org, Johannes Weiner , LKML Subject: Re: [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM Message-ID: <20190113173309.GA1578@dhcp22.suse.cz> References: <201901102359.x0ANxIbn020225@www262.sakura.ne.jp> <20190111113354.GD14956@dhcp22.suse.cz> <0d67b389-91e2-18ab-b596-39361b895c89@i-love.sakura.ne.jp> <20190111133401.GA6997@dhcp22.suse.cz> <20190111150703.GI14956@dhcp22.suse.cz> <20190111164536.GJ14956@dhcp22.suse.cz> <0aacad13-3e91-646a-90b1-c70993b05701@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0aacad13-3e91-646a-90b1-c70993b05701@i-love.sakura.ne.jp> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 12-01-19 19:52:50, Tetsuo Handa wrote: > On 2019/01/12 1:45, Michal Hocko wrote: > >>> Anyway, could you update your patch and abstract > >>> if (unlikely(tsk_is_oom_victim(current) || > >>> fatal_signal_pending(current) || > >>> current->flags & PF_EXITING)) > >>> > >>> in try_charge and reuse it in mem_cgroup_out_of_memory under the > >>> oom_lock with an explanation please? > >> > >> I don't think doing so makes sense, for > >> > >> tsk_is_oom_victim(current) = T && fatal_signal_pending(current) == F > >> > >> can't happen for mem_cgroup_out_of_memory() under the oom_lock, and > >> current->flags cannot get PF_EXITING when current is inside > >> mem_cgroup_out_of_memory(). fatal_signal_pending(current) alone is > >> appropriate for mem_cgroup_out_of_memory() under the oom_lock because > >> > >> tsk_is_oom_victim(current) = F && fatal_signal_pending(current) == T > >> > >> can happen there. > > > > I meant to use the same check consistently. If we can bypass the charge > > under a list of conditions in the charge path we should be surely be > > able to the the same for the oom path. I will not insist but unless > > there is a strong reason I would prefer that. > > > > You mean something like this? I'm not sure this change is safe. > > mm/memcontrol.c | 27 +++++++++++++++++++++++---- > 1 file changed, 23 insertions(+), 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 17189da..1733d019 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -248,6 +248,12 @@ enum res_type { > iter != NULL; \ > iter = mem_cgroup_iter(NULL, iter, NULL)) > > +static inline bool can_ignore_limit(void) > +{ > + return tsk_is_oom_victim(current) || fatal_signal_pending(current) || > + (current->flags & PF_EXITING); > +} > + > /* Some nice accessors for the vmpressure. */ > struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg) > { > @@ -1395,7 +1401,7 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, > * A few threads which were not waiting at mutex_lock_killable() can > * fail to bail out. Therefore, check again after holding oom_lock. > */ > - ret = fatal_signal_pending(current) || out_of_memory(&oc); > + ret = can_ignore_limit() || out_of_memory(&oc); > mutex_unlock(&oom_lock); > return ret; > } > @@ -2215,9 +2230,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, > * bypass the last charges so that they can exit quickly and > * free their memory. > */ > - if (unlikely(tsk_is_oom_victim(current) || > - fatal_signal_pending(current) || > - current->flags & PF_EXITING)) > + if (unlikely(can_ignore_limit())) > goto force; > > /* I meant something as simple as this, indeed. I would just s@can_ignore_limit@should_force_charge@ but this is a minor thing. -- Michal Hocko SUSE Labs