From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id 4E5998E0002 for ; Sun, 13 Jan 2019 12:36:06 -0500 (EST) Received: by mail-ed1-f69.google.com with SMTP id t7so8063847edr.21 for ; Sun, 13 Jan 2019 09:36:06 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o12si7391696edi.351.2019.01.13.09.36.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 13 Jan 2019 09:36:04 -0800 (PST) Date: Sun, 13 Jan 2019 18:36:03 +0100 From: Michal Hocko 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> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: Andrew Morton , linux-mm@kvack.org, Johannes Weiner , LKML 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