From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id D2D616B01D7 for ; Wed, 16 Jun 2010 08:25:37 -0400 (EDT) Date: Wed, 16 Jun 2010 14:24:03 +0200 From: Oleg Nesterov Subject: Re: [PATCH 6/9] oom: use same_thread_group instead comparing ->mm Message-ID: <20100616122403.GA5304@redhat.com> References: <20100616201948.72D7.A69D9226@jp.fujitsu.com> <20100616203319.72E6.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100616203319.72E6.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: LKML , linux-mm , Andrew Morton , David Rientjes , KAMEZAWA Hiroyuki List-ID: On 06/16, KOSAKI Motohiro wrote: > > Now, oom are using "child->mm != p->mm" check to distinguish subthread. Heh. is it true??? I never undestood what oom_kill_process()->list_for_each_entry() is supposed to do. > But It's incorrect. vfork() child also have the same ->mm. Yes. > This patch change to use same_thread_group() instead. I don't think we need same_thread_group(). Please note that any children must be from the different thread_group. So, > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -161,7 +161,7 @@ unsigned long oom_badness(struct task_struct *p, unsigned long uptime) > list_for_each_entry(c, &t->children, sibling) { > child = find_lock_task_mm(c); > if (child) { > - if (child->mm != p->mm) > + if (same_thread_group(p, child)) > points += child->mm->total_vm/2 + 1; > task_unlock(child); > } > @@ -486,7 +486,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, > list_for_each_entry(child, &t->children, sibling) { > unsigned long child_points; > > - if (child->mm == p->mm) > + if (same_thread_group(p, child)) > continue; In both cases same_thread_group() must be false. This means that the change in oom_badness() doesn't look right, "child->mm != p->mm" is the correct check to decide whether we should account child->mm. The change in oom_kill_process() merely removes this "continue". Could someone please explain what this code _should_ do? Oleg. -- 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