Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753189Ab1F1XXQ (ORCPT ); Tue, 28 Jun 2011 19:23:16 -0400 Received: from mail-qy0-f174.google.com ([209.85.216.174]:56979 "EHLO mail-qy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751777Ab1F1XXL convert rfc822-to-8bit (ORCPT ); Tue, 28 Jun 2011 19:23:11 -0400 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 To: Mel Gorman Cc: Andrew Morton , "P?draig Brady" , James Bottomley , Colin King , Andrew Lutomirski , Rik van Riel , Johannes Weiner , linux-mm , linux-kernel Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2377 Lines: 61 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: Pádraig Brady >> > Signed-off-by: Mel Gorman >> > --- >> >  mm/vmscan.c |    2 +- >> >  1 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 *pgdat, int order, long remaining, >> >                } >> > >> >                if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), >> > -                                                       classzone_idx, 0)) >> > +                                                       i, 0)) >> >> Isn't it  better 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. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/