Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753460Ab2KTXd1 (ORCPT ); Tue, 20 Nov 2012 18:33:27 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:39891 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751594Ab2KTXd0 (ORCPT ); Tue, 20 Nov 2012 18:33:26 -0500 Date: Tue, 20 Nov 2012 15:33:24 -0800 From: Andrew Morton To: Mel Gorman Cc: Rafael Aquini , linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , "Michael S. Tsirkin" , Rik van Riel , Andi Kleen , Konrad Rzeszutek Wilk , Minchan Kim , Peter Zijlstra , "Paul E. McKenney" Subject: Re: [PATCH v11 4/7] mm: introduce compaction and migration for ballooned pages Message-Id: <20121120153324.7119bd3b.akpm@linux-foundation.org> In-Reply-To: <20121109121602.GQ3886@csn.ul.ie> References: <08be4346b620ae9344691cc6c2ad0bc51f492e01.1352256088.git.aquini@redhat.com> <20121109121602.GQ3886@csn.ul.ie> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2032 Lines: 53 On Fri, 9 Nov 2012 12:16:02 +0000 Mel Gorman wrote: > On Wed, Nov 07, 2012 at 01:05:51AM -0200, Rafael Aquini wrote: > > Memory fragmentation introduced by ballooning might reduce significantly > > the number of 2MB contiguous memory blocks that can be used within a guest, > > thus imposing performance penalties associated with the reduced number of > > transparent huge pages that could be used by the guest workload. > > > > This patch introduces the helper functions as well as the necessary changes > > to teach compaction and migration bits how to cope with pages which are > > part of a guest memory balloon, in order to make them movable by memory > > compaction procedures. > > > > ... > > > --- a/mm/compaction.c > > +++ b/mm/compaction.c > > @@ -14,6 +14,7 @@ > > #include > > #include > > #include > > +#include > > #include "internal.h" > > > > #if defined CONFIG_COMPACTION || defined CONFIG_CMA > > @@ -565,9 +566,24 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > > goto next_pageblock; > > } > > > > - /* Check may be lockless but that's ok as we recheck later */ > > - if (!PageLRU(page)) > > + /* > > + * Check may be lockless but that's ok as we recheck later. > > + * It's possible to migrate LRU pages and balloon pages > > + * Skip any other type of page > > + */ > > + if (!PageLRU(page)) { > > + if (unlikely(balloon_page_movable(page))) { > > Because it's lockless, it really seems that the barrier stuck down there > is unnecessary. At worst you get a temporarily incorrect answer that you > recheck later under page lock in balloon_page_isolate. What happened with this? Also: what barrier? -- 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/