From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id D22D96B01B0 for ; Wed, 16 Jun 2010 11:31:28 -0400 (EDT) Received: by pwi7 with SMTP id 7so4341249pwi.14 for ; Wed, 16 Jun 2010 08:31:27 -0700 (PDT) Date: Thu, 17 Jun 2010 00:31:20 +0900 From: Minchan Kim Subject: Re: [PATCH 9/9] oom: give the dying task a higher priority Message-ID: <20100616153120.GH9278@barrios-desktop> References: <20100616201948.72D7.A69D9226@jp.fujitsu.com> <20100616203517.72EF.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100616203517.72EF.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: LKML , linux-mm , Andrew Morton , David Rientjes , KAMEZAWA Hiroyuki , "Luis Claudio R. Goncalves" , Oleg Nesterov List-ID: On Wed, Jun 16, 2010 at 08:36:29PM +0900, KOSAKI Motohiro wrote: > > From: Luis Claudio R. Goncalves > > In a system under heavy load it was observed that even after the > oom-killer selects a task to die, the task may take a long time to die. > > Right after sending a SIGKILL to the task selected by the oom-killer > this task has it's priority increased so that it can exit() exit soon, > freeing memory. That is accomplished by: > > /* > * We give our sacrificial lamb high priority and access to > * all the memory it needs. That way it should be able to > * exit() and clear out its resources quickly... > */ > p->rt.time_slice = HZ; > set_tsk_thread_flag(p, TIF_MEMDIE); > > It sounds plausible giving the dying task an even higher priority to be > sure it will be scheduled sooner and free the desired memory. It was > suggested on LKML using SCHED_FIFO:1, the lowest RT priority so that > this task won't interfere with any running RT task. > > If the dying task is already an RT task, leave it untouched. > Another good suggestion, implemented here, was to avoid boosting the > dying task priority in case of mem_cgroup OOM. > > Signed-off-by: Luis Claudio R. Goncalves > Cc: Minchan Kim > Signed-off-by: KOSAKI Motohiro > --- > mm/oom_kill.c | 38 +++++++++++++++++++++++++++++++++++--- > 1 files changed, 35 insertions(+), 3 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 7e9942d..1ecfc7a 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -82,6 +82,28 @@ static bool has_intersects_mems_allowed(struct task_struct *tsk, > #endif /* CONFIG_NUMA */ > > /* > + * If this is a system OOM (not a memcg OOM) and the task selected to be > + * killed is not already running at high (RT) priorities, speed up the > + * recovery by boosting the dying task to the lowest FIFO priority. > + * That helps with the recovery and avoids interfering with RT tasks. > + */ > +static void boost_dying_task_prio(struct task_struct *p, > + struct mem_cgroup *mem) > +{ > + struct sched_param param = { .sched_priority = 1 }; > + > + if (mem) > + return; > + > + if (rt_task(p)) { > + p->rt.time_slice = HZ; > + return; I have a question from long time ago. If we change rt.time_slice _without_ setscheduler, is it effective? I mean scheduler pick up the task faster than other normal task? > + } > + > + sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m); > +} > + > +/* -- Kind regards, Minchan Kim -- 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