From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vb0-f80.google.com (mail-vb0-f80.google.com [209.85.212.80]) by kanga.kvack.org (Postfix) with ESMTP id 5CB816B0036 for ; Sat, 16 Nov 2013 09:44:27 -0500 (EST) Received: by mail-vb0-f80.google.com with SMTP id w8so45001vbj.3 for ; Sat, 16 Nov 2013 06:44:27 -0800 (PST) Received: from psmtp.com ([74.125.245.107]) by mx.google.com with SMTP id mj9si25647851pab.16.2013.11.13.15.34.31 for ; Wed, 13 Nov 2013 15:34:32 -0800 (PST) Date: Wed, 13 Nov 2013 18:34:19 -0500 From: Johannes Weiner Subject: Re: [patch] mm, memcg: add memory.oom_control notification for system oom Message-ID: <20131113233419.GJ707@cmpxchg.org> References: <20131031054942.GA26301@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Andrew Morton , Michal Hocko , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org On Wed, Nov 13, 2013 at 02:19:00PM -0800, David Rientjes wrote: > On Thu, 31 Oct 2013, Johannes Weiner wrote: > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > > --- a/include/linux/memcontrol.h > > > +++ b/include/linux/memcontrol.h > > > @@ -155,6 +155,7 @@ static inline bool task_in_memcg_oom(struct task_struct *p) > > > } > > > > > > bool mem_cgroup_oom_synchronize(bool wait); > > > +void mem_cgroup_root_oom_notify(void); > > > > > > #ifdef CONFIG_MEMCG_SWAP > > > extern int do_swap_account; > > > @@ -397,6 +398,10 @@ static inline bool mem_cgroup_oom_synchronize(bool wait) > > > return false; > > > } > > > > > > +static inline void mem_cgroup_root_oom_notify(void) > > > +{ > > > +} > > > + > > > static inline void mem_cgroup_inc_page_stat(struct page *page, > > > enum mem_cgroup_stat_index idx) > > > { > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > > --- a/mm/memcontrol.c > > > +++ b/mm/memcontrol.c > > > @@ -5641,6 +5641,15 @@ static void mem_cgroup_oom_notify(struct mem_cgroup *memcg) > > > mem_cgroup_oom_notify_cb(iter); > > > } > > > > > > +/* > > > + * Notify any process waiting on the root memcg's memory.oom_control, but do not > > > + * notify any child memcgs to avoid triggering their per-memcg oom handlers. > > > + */ > > > +void mem_cgroup_root_oom_notify(void) > > > +{ > > > + mem_cgroup_oom_notify_cb(root_mem_cgroup); > > > +} > > > + > > > static int mem_cgroup_usage_register_event(struct cgroup_subsys_state *css, > > > struct cftype *cft, struct eventfd_ctx *eventfd, const char *args) > > > { > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > > --- a/mm/oom_kill.c > > > +++ b/mm/oom_kill.c > > > @@ -632,6 +632,10 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, > > > return; > > > } > > > > > > + /* Avoid waking up processes for oom kills triggered by sysrq */ > > > + if (!force_kill) > > > + mem_cgroup_root_oom_notify(); > > > > We have an API for global OOM notifications, please just use > > register_oom_notifier() instead. > > > > We can't use register_oom_notifier() because we don't want to notify the > root memcg for a system oom handler if existing oom notifiers free memory > (powerpc or s390). We also don't want to notify the root memcg when > current is exiting or has a pending SIGKILL, we just want to silently give > it access to memory reserves and exit. The mem_cgroup_root_oom_notify() > here is placed correctly. This is all handwaving. Somebody called out_of_memory() after they failed reclaim, the machine is OOM. The fact that current is exiting without requiring a kill is coincidental and irrelevant. You want an OOM notification, use the OOM notifiers, that's what they're for. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org