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 ESMTP id 19AA76B004D for ; Thu, 2 Sep 2010 04:51:34 -0400 (EDT) Date: Thu, 2 Sep 2010 09:51:18 +0100 From: Mel Gorman Subject: Re: [PATCH 2/3] mm: page allocator: Calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake Message-ID: <20100902085118.GA7670@csn.ul.ie> References: <1283276257-1793-1-git-send-email-mel@csn.ul.ie> <1283276257-1793-3-git-send-email-mel@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: Andrew Morton , Linux Kernel List , linux-mm@kvack.org, Rik van Riel , Johannes Weiner , Minchan Kim , KAMEZAWA Hiroyuki , KOSAKI Motohiro List-ID: On Wed, Sep 01, 2010 at 07:43:41PM -0500, Christoph Lameter wrote: > On Tue, 31 Aug 2010, Mel Gorman wrote: > > > +#ifdef CONFIG_SMP > > +/* Called when a more accurate view of NR_FREE_PAGES is needed */ > > +unsigned long zone_nr_free_pages(struct zone *zone) > > +{ > > + unsigned long nr_free_pages = zone_page_state(zone, NR_FREE_PAGES); > > You cannot call zone_page_state here because zone_page_state clips the > counter at zero. The nr_free_pages needs to reflect the unclipped state > and then the deltas need to be added. Then the clipping at zero can be > done. > Good point. This justifies the use of a generic helper that is co-located with vmstat.h. I've taken your zone_page_state_snapshot() patch, am using the helper to take a more accurate reading of NR_FREE_PAGES and preparing for a test. Thanks Christoph. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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