Re: [Qemu-devel] [PATCH v2 1/2] net: introduce MAC_TABLE_CHANGED event

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 23 May 2013 20:18:34 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> 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" <mst@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.

Would you mind to elaborate? I'm not sure I understand how this answers
my questions.