Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758115Ab1EXB6d (ORCPT ); Mon, 23 May 2011 21:58:33 -0400 Received: from smtp-out.google.com ([216.239.44.51]:29371 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758087Ab1EXB6b (ORCPT ); Mon, 23 May 2011 21:58:31 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version:content-type; b=hzSxCHiU0s7FVClvAn03qZVMkRUrqngZhMJBkMOPZbpLbAt8ziwelRzildsNncny5z +awi4lIHuPv/2l0xLtCg== Date: Mon, 23 May 2011 18:58:26 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: KOSAKI Motohiro 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 In-Reply-To: <4DDB1028.7000600@jp.fujitsu.com> Message-ID: References: <4DD61F80.1020505@jp.fujitsu.com> <4DD6207E.1070300@jp.fujitsu.com> <4DDB0B45.2080507@jp.fujitsu.com> <4DDB1028.7000600@jp.fujitsu.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1873 Lines: 39 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. -- 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/