From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 3D29D6B0044 for ; Tue, 15 Dec 2009 13:43:38 -0500 (EST) Subject: Re: [PATCH 4/8] Use prepare_to_wait_exclusive() instead prepare_to_wait() From: Mike Galbraith In-Reply-To: <4B27A417.3040206@redhat.com> References: <20091214212936.BBBA.A69D9226@jp.fujitsu.com> <4B264CCA.5010609@redhat.com> <20091215085631.CDAD.A69D9226@jp.fujitsu.com> <1260855146.6126.30.camel@marge.simson.net> <4B27A417.3040206@redhat.com> Content-Type: text/plain Date: Tue, 15 Dec 2009 19:43:30 +0100 Message-Id: <1260902610.5913.19.camel@marge.simson.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Rik van Riel Cc: KOSAKI Motohiro , lwoodman@redhat.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, minchan.kim@gmail.com List-ID: On Tue, 2009-12-15 at 09:58 -0500, Rik van Riel wrote: > On 12/15/2009 12:32 AM, Mike Galbraith wrote: > > On Tue, 2009-12-15 at 09:45 +0900, KOSAKI Motohiro wrote: > >>> On 12/14/2009 07:30 AM, KOSAKI Motohiro wrote: > >>>> if we don't use exclusive queue, wake_up() function wake _all_ waited > >>>> task. This is simply cpu wasting. > >>>> > >>>> Signed-off-by: KOSAKI Motohiro > >>> > >>>> if (zone_watermark_ok(zone, sc->order, low_wmark_pages(zone), > >>>> 0, 0)) { > >>>> - wake_up(wq); > >>>> + wake_up_all(wq); > >>>> finish_wait(wq,&wait); > >>>> sc->nr_reclaimed += sc->nr_to_reclaim; > >>>> return -ERESTARTSYS; > >>> > >>> I believe we want to wake the processes up one at a time > >>> here. > > >> Actually, wake_up() and wake_up_all() aren't different so much. > >> Although we use wake_up(), the task wake up next task before > >> try to alloate memory. then, it's similar to wake_up_all(). > > That is a good point. Maybe processes need to wait a little > in this if() condition, before the wake_up(). That would give > the previous process a chance to allocate memory and we can > avoid waking up too many processes. Pondering, I think I'd at least wake NR_CPUS. If there's not enough to go round, oh darn, but if there is, you have full utilization quicker. $.02. -Mike -- 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/ . Don't email: email@kvack.org