From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta8.messagelabs.com (mail6.bemta8.messagelabs.com [216.82.243.55]) by kanga.kvack.org (Postfix) with ESMTP id 12DFE6B0012 for ; Mon, 23 May 2011 21:58:33 -0400 (EDT) Received: from wpaz5.hot.corp.google.com (wpaz5.hot.corp.google.com [172.24.198.69]) by smtp-out.google.com with ESMTP id p4O1wUEQ002026 for ; Mon, 23 May 2011 18:58:30 -0700 Received: from pvc30 (pvc30.prod.google.com [10.241.209.158]) by wpaz5.hot.corp.google.com with ESMTP id p4O1wSGx023525 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Mon, 23 May 2011 18:58:29 -0700 Received: by pvc30 with SMTP id 30so3701661pvc.34 for ; Mon, 23 May 2011 18:58:28 -0700 (PDT) Date: Mon, 23 May 2011 18:58:26 -0700 (PDT) From: David Rientjes 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: 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 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, 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