From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rafael Aquini Subject: Re: [PATCH v4 1/3] mm: introduce compaction and migration for virtio ballooned pages Date: Fri, 3 Aug 2012 09:26:57 -0300 Message-ID: <20120803122656.GB1848__41083.7781885222$1343996871$gmane$org@t510.redhat.com> References: <49f828a9331c9b729fcf77226006921ec5bc52fa.1342485774.git.aquini@redhat.com> <20120718054824.GA32341@bbox> <20120720194858.GA16249@t510.redhat.com> <20120723023332.GA6832@bbox> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20120723023332.GA6832@bbox> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Minchan Kim Cc: Rik van Riel , Konrad Rzeszutek Wilk , "Michael S. Tsirkin" , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, Andi Kleen , Andrew Morton , Rafael Aquini List-Id: virtualization@lists.linuxfoundation.org On Mon, Jul 23, 2012 at 11:33:32AM +0900, Minchan Kim wrote: > Look at memory-hotplug, offline_page calls has_unmovable_pages, scan_lru_pages > and do_migrate_range which calls isolate_lru_page. They consider only LRU pages > to migratable ones. > As promised, I looked into those bits. Yes, they only isolate LRU pages, and as such, having this series merged or not doesn't change a bit for that code path. In fact, having this series merged and teaching hotplug's offline_pages()/do_migrate_rage() about ballooned pages might be extremely beneficial in the rare event offlining memory stumbles across a balloon page. As Rik said, I believe this is something we can look into in the near future. > IMHO, better approach is that after we can get complete free pageblocks > by compaction or reclaim, move balloon pages into that pageblocks and make > that blocks to unmovable. It can prevent fragmentation and it makes > current or future code don't need to consider balloon page. > I totally agree with Rik on this one, as well. This is the wrong approach here. All that said, I'll soon respin a v5 based on your comments on branch hinting and commentary improvements, as well as addressing AKPM's concerns. I'll also revert isolate_balloon_page() last changes back to make it a public symbol again, as (I believe) we'll shortly be using it for letting hotplug bits aware of how to isolate ballooned pages.