Re: [Qemu-devel] [Qemu-ppc] broken incoming migration

[Paolo Bonzini]

Il 12/06/2013 10:11, Benjamin Herrenschmidt ha scritto:
> On Wed, 2013-06-12 at 10:00 -0400, Paolo Bonzini wrote:
>> The only bug we have is not a performance bug related to compression;
>> it's that writing zero pages breaks overcommit.  Let's fix that, and
>> only that.
> 
> Right, do we have a way to madvise "throw away" these instead ?

We already do that, but apparently that madvise is asynchronous.

> Or do we
> have a way to track that the platform init code did write something
> there and only clear *those* pages ?

No need for; since it's copy-on-write, not copy-on-read :) we can just
check for pages that are zero and not rewrite them with zeros.  That's
what Peter's patches do, I'll review them right away.

Paolo