From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id D1FFB6B0044 for ; Tue, 15 Dec 2009 09:58:39 -0500 (EST) Message-ID: <4B27A417.3040206@redhat.com> Date: Tue, 15 Dec 2009 09:58:31 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 4/8] Use prepare_to_wait_exclusive() instead prepare_to_wait() References: <20091214212936.BBBA.A69D9226@jp.fujitsu.com> <4B264CCA.5010609@redhat.com> <20091215085631.CDAD.A69D9226@jp.fujitsu.com> <1260855146.6126.30.camel@marge.simson.net> In-Reply-To: <1260855146.6126.30.camel@marge.simson.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Mike Galbraith 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 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. > What happens to waiters should running tasks not allocate for a while? When a waiter is woken up, it will either: 1) see that there is enough free memory and wake up the next guy, or 2) run shrink_zone and wake up the next guy Either way, the processes that just got woken up will ensure that the sleepers behind them in the queue will get woken up. -- All rights reversed. -- 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