From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id C69356B0044 for ; Mon, 14 Dec 2009 20:13:51 -0500 (EST) Received: by pwi1 with SMTP id 1so2911423pwi.6 for ; Mon, 14 Dec 2009 17:13:49 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20091215090441.CDB0.A69D9226@jp.fujitsu.com> References: <20091214213026.BBBD.A69D9226@jp.fujitsu.com> <20091215084636.c7790658.minchan.kim@barrios-desktop> <20091215090441.CDB0.A69D9226@jp.fujitsu.com> Date: Tue, 15 Dec 2009 10:13:48 +0900 Message-ID: <28c262360912141713t6e0e5915m3bb30aa099914c40@mail.gmail.com> Subject: Re: [PATCH 5/8] Use io_schedule() instead schedule() From: Minchan Kim Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Rik van Riel , lwoodman@redhat.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Tue, Dec 15, 2009 at 9:56 AM, KOSAKI Motohiro wrote: >> 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 >> > --- >> > =C2=A0mm/vmscan.c | =C2=A0 =C2=A02 +- >> > =C2=A01 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) >> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 max_zone_concu= rrent_reclaimers) >> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = break; >> > >> > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 schedule(); >> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 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. I confused it. Thanks for correcting me. :) > >> In addition, if system doesn't have swap device space and out of page ca= che >> due to heavy memory pressue, VM might scan & drop pages until priority i= s 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 pre= ssure. I > don't hope change this without reasonable reason. 2. iowait makes schedul= er > bonus a bit, vmscan task should have many time slice than memory consume > task. it improve VM stabilization. AFAIK, CFS scheduler doesn't give the bonus to I/O wait task any more. > > but I agree the benefit isn't so big. if we have reasonable reason, I > don't oppose use schedule(). > > > > --=20 Kind regards, Minchan Kim -- 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