Re: [Qemu-devel] [RFC PATCH RDMA support v1: 10/13] introduce new command migrate_check_for_zero

[Michael R. Hines]

On 04/11/2013 07:13 AM, Michael S. Tsirkin wrote:
> On Thu, Apr 11, 2013 at 11:18:38AM +0200, Paolo Bonzini wrote:
> > Il 11/04/2013 09:38, Michael S. Tsirkin ha scritto:
> > > On Wed, Apr 10, 2013 at 06:28:18PM -0400, address@hidden wrote:
> > > > From: "Michael R. Hines" <address@hidden>
> > > >
> > > > This allows the user to disable zero page checking during migration
> > > >
> > > > Signed-off-by: Michael R. Hines <address@hidden>
> > > IMO this knob is too low level to expose to management.
> > > Why not disable this automatically when migrating with rdma?
> > Thinking more about it, I'm not sure why it is important to disable it.
> This just illustrates the point. There's no place for such low level
> knobs in the management interface.

I disagree with that: We already have precedent for this in the
XBZRLE capability. Zero page checking is no "more" low-level than this
capability already is and the community has already agreed to expose
this capability to management.

Since zero page scanning does in fact affect performance, we not give
the user the option?

Why would the community agree to expose one low-level feature and not 
expose another?

- Michael