From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754049Ab0CIJx6 (ORCPT ); Tue, 9 Mar 2010 04:53:58 -0500 Received: from cantor2.suse.de ([195.135.220.15]:39029 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753924Ab0CIJxx (ORCPT ); Tue, 9 Mar 2010 04:53:53 -0500 Date: Tue, 9 Mar 2010 20:53:42 +1100 From: Nick Piggin To: Mel Gorman Cc: linux-mm@kvack.org, Christian Ehrhardt , Chris Mason , Jens Axboe , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] page-allocator: Check zone pressure when batch of pages are freed Message-ID: <20100309095342.GD8653@laptop> References: <1268048904-19397-1-git-send-email-mel@csn.ul.ie> <1268048904-19397-3-git-send-email-mel@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1268048904-19397-3-git-send-email-mel@csn.ul.ie> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Cool, you found this doesn't hurt performance too much? Can't you remove the check from the reclaim code now? (The check here should give a more timely wait anyway) This is good because it should eliminate most all cases of extra waiting. I wonder if you've also thought of doing the check in the allocation path too as we were discussing? (this would give a better FIFO behaviour under memory pressure but I could easily agree it is not worth the cost) On Mon, Mar 08, 2010 at 11:48:22AM +0000, Mel Gorman wrote: > When a batch of pages have been freed to the buddy allocator, it is possible > that it is enough to push a zone above its watermarks. This patch puts a > check in the free path for zone pressure. It's in a common path but for > the most part, it should only be checking if a linked list is empty and > have minimal performance impact. > > Signed-off-by: Mel Gorman > --- > mm/page_alloc.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 1383ff9..3c8e8b7 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -562,6 +562,9 @@ static void free_pcppages_bulk(struct zone *zone, int count, > } while (--count && --batch_free && !list_empty(list)); > } > spin_unlock(&zone->lock); > + > + /* A batch of pages have been freed so check zone pressure */ > + check_zone_pressure(zone); > } > > static void free_one_page(struct zone *zone, struct page *page, int order, > -- > 1.6.5