From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx105.postini.com [74.125.245.105]) by kanga.kvack.org (Postfix) with SMTP id 76C316B002B for ; Sun, 26 Aug 2012 10:41:03 -0400 (EDT) Message-ID: <503A3565.2060004@redhat.com> Date: Sun, 26 Aug 2012 10:40:37 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH v9 0/5] make balloon pages movable by compaction References: <20120826075840.GE19551@redhat.com> In-Reply-To: <20120826075840.GE19551@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Michael S. Tsirkin" Cc: Rafael Aquini , linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , Mel Gorman , Andi Kleen , Andrew Morton , Konrad Rzeszutek Wilk , Minchan Kim , Peter Zijlstra , "Paul E. McKenney" On 08/26/2012 03:58 AM, Michael S. Tsirkin wrote: > On Sat, Aug 25, 2012 at 02:24:55AM -0300, 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-set follows the main idea discussed at 2012 LSFMMS session: >> "Ballooning for transparent huge pages" -- http://lwn.net/Articles/490114/ >> to introduce the required changes to the virtio_balloon driver, as well as >> the changes to the core compaction & migration bits, in order to make those >> subsystems aware of ballooned pages and allow memory balloon pages become >> movable within a guest, thus avoiding the aforementioned fragmentation issue > > Meta-question: are there any numbers showing gain from this patchset? > > The reason I ask, on migration we notify host about each page > individually. If this is rare maybe the patchset does not help much. > If this is common we would be better off building up a list of multiple > pages and passing them in one go. The gain is in getting a better THP allocation rate inside the guest, allowing applications to run faster. The rarer it is for this code to run, the better - it means we are getting the benefits without the overhead :) -- All rights reversed -- 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