Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758128Ab1EXCDp (ORCPT ); Mon, 23 May 2011 22:03:45 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:39995 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751188Ab1EXCDl (ORCPT ); Mon, 23 May 2011 22:03:41 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Message-ID: <4DDB11F4.2070903@jp.fujitsu.com> Date: Tue, 24 May 2011 11:03:32 +0900 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; ja; rv:1.9.2.17) Gecko/20110414 Lightning/1.0b2 Thunderbird/3.1.10 MIME-Version: 1.0 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 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: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1965 Lines: 45 (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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/