From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 61C616B0100 for ; Tue, 28 Jun 2011 19:23:14 -0400 (EDT) Received: by qwa26 with SMTP id 26so511738qwa.14 for ; Tue, 28 Jun 2011 16:23:10 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20110628125249.GX9396@suse.de> References: <1308926697-22475-1-git-send-email-mgorman@suse.de> <1308926697-22475-4-git-send-email-mgorman@suse.de> <20110628125249.GX9396@suse.de> Date: Wed, 29 Jun 2011 08:23:10 +0900 Message-ID: Subject: Re: [PATCH 3/4] mm: vmscan: Evaluate the watermarks against the correct classzone From: Minchan Kim Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Andrew Morton , P?draig Brady , James Bottomley , Colin King , Andrew Lutomirski , Rik van Riel , Johannes Weiner , linux-mm , linux-kernel On Tue, Jun 28, 2011 at 9:52 PM, Mel Gorman wrote: > On Mon, Jun 27, 2011 at 03:53:04PM +0900, Minchan Kim wrote: >> On Fri, Jun 24, 2011 at 11:44 PM, Mel Gorman wrote: >> > When deciding if kswapd is sleeping prematurely, the classzone is >> > taken into account but this is different to what balance_pgdat() and >> > the allocator are doing. Specifically, the DMA zone will be checked >> > based on the classzone used when waking kswapd which could be for a >> > GFP_KERNEL or GFP_HIGHMEM request. The lowmem reserve limit kicks in, >> > the watermark is not met and kswapd thinks its sleeping prematurely >> > keeping kswapd awake in error. >> >> >> I thought it was intentional when you submitted a patch firstly. > > It was, it also wasn't right. > >> "Kswapd makes sure zones include enough free pages(ie, include reserve >> limit of above zones). >> But you seem to see DMA zone can't meet above requirement forever in >> some situation so that kswapd doesn't sleep. >> Right? >> > > Right. > >> > >> > Reported-and-tested-by: P=C3=A1draig Brady >> > Signed-off-by: Mel Gorman >> > --- >> > =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 9cebed1..a76b6cc2 100644 >> > --- a/mm/vmscan.c >> > +++ b/mm/vmscan.c >> > @@ -2341,7 +2341,7 @@ static bool sleeping_prematurely(pg_data_t *pgda= t, int order, long remaining, >> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0} >> > >> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0if (!zone_water= mark_ok_safe(zone, order, high_wmark_pages(zone), >> > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 classzone_idx, 0)) >> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 i, 0)) >> >> Isn't it =C2=A0better to use 0 instead of i? >> > > I considered it but went with i to compromise between making sure zones > included enough free pages without requiring that ZONE_DMA meet an > almost impossible requirement when under continual memory pressure. I see. Thanks, Mel. --=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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org