Re: Elvis upstreaming plan

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Nov 27, 2013 at 01:05:40PM +0200, Abel Gordon wrote:
> > > (CCing Eyal Moscovici who is actually prototyping with multiple
> > > policies and may want to join this thread)
> > >
> > > Starting with basic policies: we can use a single vhost thread
> > > and create new vhost threads if it becomes saturated and there
> > > are enough cpu cycles available in the system
> > > or if the latency (how long the requests in the virtio queues wait
> > > until they are handled) is too high.
> > > We can merge threads if the latency is already low or if the threads
> > > are not saturated.
> > >
> > > There is a hidden trade-off here: when you run more vhost threads you
> > > may actually be stealing cpu cycles from the vcpu threads and also
> > > increasing context switches. So, from the vhost perspective it may
> > > improve performance but from the vcpu threads perspective it may
> > > degrade performance.
> >
> > So this is a very interesting problem to solve but what does
> > management know that suggests it can solve it better?
> 
> Yep, and Eyal is currently working on this.
> What the management knows ? depends who the management is :)
> Could be just I/O activity (black-box: I/O request rate, I/O
> handling rate, latency)

We know much more about this than managament, don't we?

> or application performance (white-box).

This would have to come with a proposal for getting
this white-box info out of guest somehow.

-- 
MSR