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 5B5396B0044 for ; Mon, 14 Dec 2009 19:56:57 -0500 (EST) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id nBF0usTG025625 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Tue, 15 Dec 2009 09:56:54 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 3B27A45DE6E for ; Tue, 15 Dec 2009 09:56:54 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 1917345DE60 for ; Tue, 15 Dec 2009 09:56:54 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 0169E1DB8037 for ; Tue, 15 Dec 2009 09:56:54 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 88A7A1DB8043 for ; Tue, 15 Dec 2009 09:56:50 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 5/8] Use io_schedule() instead schedule() In-Reply-To: <20091215084636.c7790658.minchan.kim@barrios-desktop> References: <20091214213026.BBBD.A69D9226@jp.fujitsu.com> <20091215084636.c7790658.minchan.kim@barrios-desktop> Message-Id: <20091215090441.CDB0.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Tue, 15 Dec 2009 09:56:49 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: kosaki.motohiro@jp.fujitsu.com, Rik van Riel , lwoodman@redhat.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: > On Mon, 14 Dec 2009 21:30:54 +0900 (JST) > KOSAKI Motohiro wrote: > > > All task sleeping point in vmscan (e.g. congestion_wait) use > > io_schedule. then shrink_zone_begin use it too. > > > > Signed-off-by: KOSAKI Motohiro > > --- > > mm/vmscan.c | 2 +- > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 3562a2d..0880668 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -1624,7 +1624,7 @@ static int shrink_zone_begin(struct zone *zone, struct scan_control *sc) > > max_zone_concurrent_reclaimers) > > break; > > > > - schedule(); > > + io_schedule(); > > Hmm. We have many cond_resched which is not io_schedule in vmscan.c. cond_resched don't mean sleep on wait queue. it's similar to yield. > In addition, if system doesn't have swap device space and out of page cache > due to heavy memory pressue, VM might scan & drop pages until priority is zero > or zone is unreclaimable. > > I think it would be not a IO wait. two point. 1. For long time, Administrator usually watch iowait% at heavy memory pressure. I don't hope change this without reasonable reason. 2. iowait makes scheduler bonus a bit, vmscan task should have many time slice than memory consume task. it improve VM stabilization. but I agree the benefit isn't so big. if we have reasonable reason, I don't oppose use schedule(). -- 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