From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id C61EF6B005C for ; Tue, 4 Aug 2009 22:51:30 -0400 (EDT) Received: from m5.gw.fujitsu.co.jp ([10.0.50.75]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n752pZmB024455 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Wed, 5 Aug 2009 11:51:36 +0900 Received: from smail (m5 [127.0.0.1]) by outgoing.m5.gw.fujitsu.co.jp (Postfix) with ESMTP id BAB252AEA81 for ; Wed, 5 Aug 2009 11:51:35 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (s5.gw.fujitsu.co.jp [10.0.50.95]) by m5.gw.fujitsu.co.jp (Postfix) with ESMTP id 903BF1EF081 for ; Wed, 5 Aug 2009 11:51:35 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 7B2ABE1800A for ; Wed, 5 Aug 2009 11:51:35 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 320D0E1800B for ; Wed, 5 Aug 2009 11:51:32 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 1/4] oom: move oom_adj to signal_struct In-Reply-To: <20090805114004.459a7deb.minchan.kim@barrios-desktop> References: <20090805110107.5B97.A69D9226@jp.fujitsu.com> <20090805114004.459a7deb.minchan.kim@barrios-desktop> Message-Id: <20090805114650.5BA1.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Wed, 5 Aug 2009 11:51:31 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: kosaki.motohiro@jp.fujitsu.com, LKML , Paul Menage , David Rientjes , KAMEZAWA Hiroyuki , Rik van Riel , Andrew Morton , Linus Torvalds , Oleg Nesterov , linux-mm List-ID: > On Wed, 5 Aug 2009 11:29:34 +0900 (JST) > KOSAKI Motohiro wrote: > > > Hi > > > > > Hi, Kosaki. > > > > > > I am so late to invole this thread. > > > But let me have a question. > > > > > > What's advantage of placing oom_adj in singal rather than task ? > > > I mean task->oom_adj and task->signal->oom_adj ? > > > > > > I am sorry if you already discussed it at last threads. > > > > Not sorry. that's very good question. > > > > I'm trying to explain the detailed intention of commit 2ff05b2b4eac > > (move oom_adj to mm_struct). > > > > In 2.6.30, OOM logic callflow is here. > > > > __out_of_memory > > select_bad_process for each task > > badness calculate badness of one task > > oom_kill_process search child > > oom_kill_task kill target task and mm shared tasks with it > > > > example, process-A have two thread, thread-A and thread-B and it > > have very fat memory. > > And, each thread have following likes oom property. > > > > thread-A: oom_adj = OOM_DISABLE, oom_score = 0 > > thread-B: oom_adj = 0, oom_score = very-high > > > > Then, select_bad_process() select thread-B, but oom_kill_task refuse > > kill the task because thread-A have OOM_DISABLE. > > __out_of_memory() call select_bad_process() again. but select_bad_process() > > select the same task. It mean kernel fall in the livelock. > > > > The fact is, select_bad_process() must select killable task. otherwise > > OOM logic go into livelock. > > > > Is this enough explanation? thanks. > > > > Thanks for good explanation. :) > > It resulted from patch of David which moved task_struct->oom_ajd > to mm_struct. I understood it. No. It's very old problem. David's patch fixed it. It mean per-process oom_adj prevent select_bad_process() return a task in unkillable process. unfortunatelly, his patch can't treat vfork case ideally. I hope to fix it. > It meant oom_adj was not per-process. > > AFAIU, you want to make oom_adj per-process, again. > And you selected the place with task->singal as per-process. > > What I have a question is that why do you select task_struct->signal > rather than task_struct like old? > > What's benefit of using task_struct->signal ? prior Davied patch (task->oom_adj) might makes livelock. -- 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