Re: [Qemu-devel] [PATCH v8 3/8] tests: Add migration xbzrle test

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Juan Quintela (quintela@redhat.com) wrote:
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> > * Juan Quintela (quintela@redhat.com) wrote:
> >> Signed-off-by: Juan Quintela <quintela@redhat.com>
> >> Reviewed-by: Peter Xu <peterx@redhat.com>
> 
> >> +
> >> +    migrate_set_parameter(from, "xbzrle-cache-size", "33554432");
> >
> > I still worry about the cache size relative to the size of memory we're
> > actually changing in the test; I don't quite understand why it's turning
> > out to get lots of hits.
> 
> I planned this as a smorke test.  But what value do you have in mind?

Given the test code dirties 100MB of RAM, I suggest a cache of 110MB
say.  But it's interesting that the stats show we are getting a lot of
page hits; I'm not sure I understand why.

> > Also, xbzrle eats so much CPU we'll still have to watch out for the low
> > end CPUs.
> 
> Any concrete suggestion?
> 
> My plan would have been to push on my next pull request:
> 
> Add migration precopy test
> Add migration xbzrle test
> Migration ppc now inlines its program
> 
> And put the rest of the patches with fixes for another review.

Go with it and lets see; if we hit problems then we can just turn that
300ms downtime limit right up.

Dave

> 
> Later, Juan.
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK