linux-kernel - Re: [PATCH kernel 1/2] mm: add the related functions to build the free page bitmap

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Date:	Tue, 19 Apr 2016 11:26:32 -0400
From:	Rik van Riel <riel@...hat.com>
To:	"Li, Liang Z" <liang.z.li@...el.com>,
	"mst@...hat.com" <mst@...hat.com>,
	"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"quintela@...hat.com" <quintela@...hat.com>,
	"amit.shah@...hat.com" <amit.shah@...hat.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"dgilbert@...hat.com" <dgilbert@...hat.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
	"agraf@...e.de" <agraf@...e.de>,
	"borntraeger@...ibm.com" <borntraeger@...ibm.com>
Subject: Re: [PATCH kernel 1/2] mm: add the related functions to build the
 free page bitmap

On Tue, 2016-04-19 at 15:02 +0000, Li, Liang Z wrote:
> > 
> > On Tue, 2016-04-19 at 22:34 +0800, Liang Li wrote:
> > > 
> > > The free page bitmap will be sent to QEMU through virtio
> > > interface and
> > > used for live migration optimization.
> > > Drop the cache before building the free page bitmap can get more
> > > free
> > > pages. Whether dropping the cache is decided by user.
> > > 
> > How do you prevent the guest from using those recently-freed pages
> > for
> > something else, between when you build the bitmap and the live
> > migration
> > completes?
> Because the dirty page logging is enabled before building the bitmap,
> there is no need
> to prevent the guest from using the recently-freed pages ...

Fair enough.

It would be good to have that mentioned in the
changelog.