From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 962666B00B7 for ; Tue, 9 Mar 2010 05:08:56 -0500 (EST) Date: Tue, 9 Mar 2010 10:08:35 +0000 From: Mel Gorman Subject: Re: [PATCH 2/3] page-allocator: Check zone pressure when batch of pages are freed Message-ID: <20100309100835.GA4883@csn.ul.ie> References: <1268048904-19397-1-git-send-email-mel@csn.ul.ie> <1268048904-19397-3-git-send-email-mel@csn.ul.ie> <20100309095342.GD8653@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100309095342.GD8653@laptop> Sender: owner-linux-mm@kvack.org To: Nick Piggin Cc: linux-mm@kvack.org, Christian Ehrhardt , Chris Mason , Jens Axboe , linux-kernel@vger.kernel.org List-ID: On Tue, Mar 09, 2010 at 08:53:42PM +1100, Nick Piggin wrote: > Cool, you found this doesn't hurt performance too much? > Nothing outside the noise was measured. I didn't profile it to be absolutly sure but I expect it's ok. > Can't you remove the check from the reclaim code now? (The check > here should give a more timely wait anyway) > I'll try and see what the timing and total IO figures look like. > 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) > I *could* make the check but as I noted in the leader, there isn't really a good test case that determines if these changes are "good" or "bad". Removing congestion_wait() seems like an obvious win but other modifications that alter how and when processes wait are less obvious. > 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 > -- 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