Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754011Ab0BLJ6V (ORCPT ); Fri, 12 Feb 2010 04:58:21 -0500 Received: from smtp-out.google.com ([216.239.33.17]:53113 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750969Ab0BLJ6S (ORCPT ); Fri, 12 Feb 2010 04:58:18 -0500 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id: references:user-agent:mime-version:content-type:x-system-of-record; b=nI3xDZB6xeA3RGw3/9iWy6bCvhbgRvod8mO83eUkh2iTD2jbP/NClWxRQ5M/599JZ ppub5VUfRlPeuP509BJ0w== Date: Fri, 12 Feb 2010 01:58:10 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: KAMEZAWA Hiroyuki cc: Andrew Morton , Rik van Riel , Nick Piggin , Andrea Arcangeli , Balbir Singh , Lubos Lunak , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [patch 5/7 -mm] oom: replace sysctls with quick mode In-Reply-To: <20100212092634.60a76cf9.kamezawa.hiroyu@jp.fujitsu.com> Message-ID: References: <20100212092634.60a76cf9.kamezawa.hiroyu@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: 2433 Lines: 49 On Fri, 12 Feb 2010, KAMEZAWA Hiroyuki wrote: > > Two VM sysctls, oom dump_tasks and oom_kill_allocating_task, were > > implemented for very large systems to avoid excessively long tasklist > > scans. The former suppresses helpful diagnostic messages that are > > emitted for each thread group leader that are candidates for oom kill > > including their pid, uid, vm size, rss, oom_adj value, and name; this > > information is very helpful to users in understanding why a particular > > task was chosen for kill over others. The latter simply kills current, > > the task triggering the oom condition, instead of iterating through the > > tasklist looking for the worst offender. > > > > Both of these sysctls are combined into one for use on the aforementioned > > large systems: oom_kill_quick. This disables the now-default > > oom_dump_tasks and kills current whenever the oom killer is called. > > > > The oom killer rewrite is the perfect opportunity to combine both sysctls > > into one instead of carrying around the others for years to come for > > nothing else than legacy purposes. > > > > Signed-off-by: David Rientjes > > seems reasonable..but how old these APIs are ? Replacement is ok ? > I'm not concerned about /proc/sys/vm/oom_dump_tasks because it was disabled by default and is now enabled by default (unless the user sets this new /proc/sys/vm/oom_kill_quick). So existing users of oom_dump_tasks will just have their write fail but identical behavior as before. /proc/sys/vm/oom_kill_allocating_task is different since it now requires enabling /proc/sys/vm/oom_kill_quick, but I think there are such few users (SGI originally requested it a couple years ago when we started scanning the tasklist for CONSTRAINT_CPUSET in 2.6.24) and the side-effect of not enabling it is minimal, it's just a long delay at oom kill time because they must scan the tasklist. Therefore, I don't see it as a major problem that will cause large disruptions, instead I see it as a great opportunity to get rid of one more sysctl without taking away functionality. > Reviewed-by: KAMEZAWA Hiroyuki > Thanks! -- 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/