From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757377Ab2IQWPf (ORCPT ); Mon, 17 Sep 2012 18:15:35 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:56564 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757329Ab2IQWPd (ORCPT ); Mon, 17 Sep 2012 18:15:33 -0400 Date: Mon, 17 Sep 2012 15:15:31 -0700 From: Andrew Morton To: Rafael Aquini Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , "Michael S. Tsirkin" , Rik van Riel , Mel Gorman , Andi Kleen , Konrad Rzeszutek Wilk , Minchan Kim , Peter Zijlstra , "Paul E. McKenney" Subject: Re: [PATCH v10 0/5] make balloon pages movable by compaction Message-Id: <20120917151531.e9ac59f2.akpm@linux-foundation.org> In-Reply-To: References: 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 On Mon, 17 Sep 2012 13:38:15 -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 > > Following are numbers that prove this patch benefits on allowing compaction > to be more effective at memory ballooned guests. > > Results for STRESS-HIGHALLOC benchmark, from Mel Gorman's mmtests suite, > running on a 4gB RAM KVM guest which was ballooning 1gB RAM in 256mB chunks, > at every minute (inflating/deflating), while test was running: How can a patchset reach v10 and have zero Reviewed-by's? The patchset looks reasonable to me and your empirical results look good. But I don't feel that I'm in a position to decide on its overall desirability, either in a standalone sense or in comparison to any alternative schemes which anyone has proposed. IOW, Rusty and KVM folks: please consider thyself poked. I looked through the code and have some comments which are minor in the overall scheme of things. I'll be more comfortable when a compaction expert has had a go over it. IOW, Mel joins the pokee list ;) (The question of "overall desirability" is the big one here. Do we actually want to add this to Linux? The rest is details which we can work out).