On Thu, May 23, 2013 at 11:54:03AM -0400, Luiz Capitulino wrote: > On Thu, 16 May 2013 18:17:23 +0300 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > > The > > > existing throttling approach ensures that if the event includes latest > > > guest information, then the host doesn't even have to do do a query, and > > > is guaranteed that reacting to the final event will always see the most > > > recent request. But most importantly, if the existing throttling works, > > > why do we have to invent a one-off approach for this event instead of > > > reusing existing code? > > Sorry to restart this week old discussion, but I'm now reviewing the patch > in question and I dislike how we're coupling the event and the query > command. > > > Because of the 1st issue above. A large delay because we > > Has this been measured? How long is this large delay? > > Also, is it impossible for management to issue query-rx-filter > on a reasonable rate that would also cause the same problems? > IOW, how can we be sure we're fixing anything without trying it > on a real use-case scenario?
Play with priorities, you can make management arbitrarily slow. It's just not sane to assume any timing guarantees for tasks running on Linux. > > exceed an arbitrary throttling rate would be bad > > for the guest. Contrast with delay in e.g. > > device delete event. > > The throttling mechanism is good for events that host cares > > about, not for events that guest cares about. > > > > > -- > > > Eric Blake eblake redhat com +1-919-301-3266 > > > Libvirt virtualization library http://libvirt.org > > > > > > > > >
