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 ESMTP id E1A8B6B0012 for ; Mon, 23 May 2011 22:03:42 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id C2CF93EE0C0 for ; Tue, 24 May 2011 11:03:39 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id AA4A445DE6E for ; Tue, 24 May 2011 11:03:39 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 8BC3545DE4E for ; Tue, 24 May 2011 11:03:39 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 505ECE38007 for ; Tue, 24 May 2011 11:03:39 +0900 (JST) Received: from m106.s.css.fujitsu.com (m106.s.css.fujitsu.com [10.240.81.146]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 17B121DB803C for ; Tue, 24 May 2011 11:03:39 +0900 (JST) Message-ID: <4DDB11F4.2070903@jp.fujitsu.com> Date: Tue, 24 May 2011 11:03:32 +0900 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [PATCH 4/5] oom: don't kill random process References: <4DD61F80.1020505@jp.fujitsu.com> <4DD6207E.1070300@jp.fujitsu.com> <4DDB0B45.2080507@jp.fujitsu.com> <4DDB1028.7000600@jp.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: rientjes@google.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, caiqian@redhat.com, hughd@google.com, kamezawa.hiroyu@jp.fujitsu.com, minchan.kim@gmail.com, oleg@redhat.com (2011/05/24 10:58), David Rientjes wrote: > On Tue, 24 May 2011, KOSAKI Motohiro wrote: > >>>>> This is unnecessary and just makes the oom killer egregiously long. We >>>>> are already diagnosing problems here at Google where the oom killer >>>>> holds >>>>> tasklist_lock on the readside for far too long, causing other cpus >>>>> waiting >>>>> for a write_lock_irq(&tasklist_lock) to encounter issues when irqs are >>>>> disabled and it is spinning. A second tasklist scan is simply a >>>>> non-starter. >>>>> >>>>> [ This is also one of the reasons why we needed to introduce >>>>> mm->oom_disable_count to prevent a second, expensive tasklist scan. >>>>> ] >>>> >>>> You misunderstand the code. Both select_bad_process() and >>>> oom_kill_process() >>>> are under tasklist_lock(). IOW, no change lock holding time. >>>> >>> >>> A second iteration through the tasklist in select_bad_process() will >>> extend the time that tasklist_lock is held, which is what your patch does. >> >> It never happen usual case. Plz think when happen all process score = 1. >> > > I don't care if it happens in the usual case or extremely rare case. It > significantly increases the amount of time that tasklist_lock is held > which causes writelock starvation on other cpus and causes issues, > especially if the cpu being starved is updating the timer because it has > irqs disabled, i.e. write_lock_irq(&tasklist_lock) usually in the clone or > exit path. We can do better than that, and that's why I proposed my patch > to CAI that increases the resolution of the scoring and makes the root > process bonus proportional to the amount of used memory. Do I need to say the same word? Please read the code at first. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org