From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCH RFC 00/10] Xen balloon page compaction support Date: Thu, 16 Oct 2014 10:31:40 +0100 Message-ID: <543F907C.4060801@citrix.com> References: <1413388459-4663-1-git-send-email-wei.liu2@citrix.com> <543EA005.3090407@citrix.com> <20141015163044.GE29948@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20141015163044.GE29948@zion.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Wei Liu Cc: boris.ostrovsky@oracle.com, stefano.stabellini@eu.citrix.com, ian.campbell@citrix.com, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 15/10/14 17:30, Wei Liu wrote: > On Wed, Oct 15, 2014 at 05:25:41PM +0100, David Vrabel wrote: >> On 15/10/14 16:54, Wei Liu wrote: >>> Hi all >>> >>> This is a prototype to make Xen balloon driver work with balloon page >>> compaction. The goal is to reduce guest physical address space fragmentation >>> introduced by balloon pages. Having guest physical address space as contiguous >>> as possible is generally useful (because guest can have higher order pages), and >>> it should also help improve HVM performance (provided that guest kernel knows >>> how to use huge pages -- Linux has hugetlbfs and transparent huge page). >>> >>> The approach is simple. Core balloon driver is made one of the page sources of >>> Xen balloon driver. Those pages allocated from core balloon driver are subject >>> to balloon page compaction. >> >> Your page migrate function is broken. I'm not going to review anything >> else in this series until you propose a solution for this. >> > > What do you think about this idea in general? That's what I care at this > point. You can skip reviewing at the moment. In light of Andrew's comments I would like to see a design for the complete solution, including the parts necessary to coalesce or preserve superpages in the stage 2 translation tables. In particular, it looks like page migration will just fragment the stage 2 tables. David