From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 277486B01EE for ; Thu, 1 Apr 2010 04:35:10 -0400 (EDT) Received: from wpaz21.hot.corp.google.com (wpaz21.hot.corp.google.com [172.24.198.85]) by smtp-out.google.com with ESMTP id o318Z5mw019845 for ; Thu, 1 Apr 2010 01:35:05 -0700 Received: from pvc30 (pvc30.prod.google.com [10.241.209.158]) by wpaz21.hot.corp.google.com with ESMTP id o318Z4l3025762 for ; Thu, 1 Apr 2010 01:35:04 -0700 Received: by pvc30 with SMTP id 30so252317pvc.34 for ; Thu, 01 Apr 2010 01:35:04 -0700 (PDT) Date: Thu, 1 Apr 2010 01:35:02 -0700 (PDT) From: David Rientjes Subject: Re: [patch] oom: give current access to memory reserves if it has been killed In-Reply-To: <20100331204718.GD11635@redhat.com> Message-ID: References: <20100326150805.f5853d1c.akpm@linux-foundation.org> <20100326223356.GA20833@redhat.com> <20100328145528.GA14622@desktop> <20100328162821.GA16765@redhat.com> <20100329112111.GA16971@redhat.com> <20100330154659.GA12416@redhat.com> <20100331175836.GA11635@redhat.com> <20100331204718.GD11635@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Oleg Nesterov Cc: Andrew Morton , anfei , KOSAKI Motohiro , nishimura@mxp.nes.nec.co.jp, KAMEZAWA Hiroyuki , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Wed, 31 Mar 2010, Oleg Nesterov wrote: > Probably something like the patch below makes sense. Note that > "skip kernel threads" logic is wrong too, we should check PF_KTHREAD. > Probably it is better to check it in select_bad_process() instead, > near is_global_init(). > is_global_init() will be true for p->flags & PF_KTHREAD. > The new helper, find_lock_task_mm(), should be used by > oom_forkbomb_penalty() too. > > dump_tasks() doesn't need it, it does do_each_thread(). Cough, > __out_of_memory() and out_of_memory() call it without tasklist. > We are going to panic() anyway, but still. > Indeed, good observation. > Oleg. > > --- x/mm/oom_kill.c > +++ x/mm/oom_kill.c > @@ -129,6 +129,19 @@ static unsigned long oom_forkbomb_penalt > (child_rss / sysctl_oom_forkbomb_thres) : 0; > } > > +static find_lock_task_mm(struct task_struct *p) > +{ > + struct task_struct *t = p; > + do { > + task_lock(t); > + if (likely(t->mm && !(t->flags & PF_KTHREAD))) > + return t; > + task_unlock(t); > + } while_each_thred(p, t); > + > + return NULL; > +} > + > /** > * oom_badness - heuristic function to determine which candidate task to kill > * @p: task struct of which task we should calculate > @@ -159,13 +172,9 @@ unsigned int oom_badness(struct task_str > if (p->flags & PF_OOM_ORIGIN) > return 1000; > > - task_lock(p); > - mm = p->mm; > - if (!mm) { > - task_unlock(p); > + p = find_lock_task_mm(p); > + if (!p) > return 0; > - } > - > /* > * The baseline for the badness score is the proportion of RAM that each > * task's rss and swap space use. > @@ -330,12 +339,6 @@ static struct task_struct *select_bad_pr > *ppoints = 1000; > } > > - /* > - * skip kernel threads and tasks which have already released > - * their mm. > - */ > - if (!p->mm) > - continue; > if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) > continue; You can't do this for the reason I cited in another email, oom_badness() returning 0 does not exclude a task from being chosen by selcet_bad_process(), it will use that task if nothing else has been found yet. We must explicitly filter it from consideration by checking for !p->mm. -- 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