On Thu, Apr 11, 2013 at 09:19:43AM -0400, Michael R. Hines wrote: > 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, mrhi...@linux.vnet.ibm.com wrote: > >>>>From: "Michael R. Hines" <mrhi...@us.ibm.com> > >>>> > >>>>This allows the user to disable zero page checking during migration > >>>> > >>>>Signed-off-by: Michael R. Hines <mrhi...@us.ibm.com> > >>>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.
My understanding is the issue is protocol compatibility, not optimization. E.g. you can migrate to file, for each new feature you need a way to disable it to stay compatible. > 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
