[Engine-devel] [UX] how to design a bar/line chart?

[Dan Kenigsberg]

On Tue, Nov 12, 2013 at 11:49:12AM +0100, Michal Skrivanek wrote:
> 
> On Nov 12, 2013, at 11:18 , Tomas Jelinek <tjelinek at redhat.com> wrote:
> 
> > So we have looked into the resource usage sampling with mbetak and also with Michal and it seems that
> > 
> > for the CPU usage:
> > - VDSM polls libvirt to get the runtime statistics of the VM regularly. The pooling interval is configured in 
> >  vdsm.conf as vm_sample_cpu_interval and by default it is 15 seconds
> > - libvirt returns something we than use to calculate the average CPU usage since the last poll
> > - engine polls VDSM once in 15 seconds to get the current statistics (the same 15 seconds is just a coincidence and we can not count on this)
> > - than the frontend polls the engine each 5-60 seconds (depends on the refresh rate) and gets the current value from the engine
> > - the user can press the refresh button anytime to poll the engine again
> > 
> > For network usage:
> > - it should be pretty much the same as the CPU just the VDSM poll interval is configured as vm_sample_net_interval and by default it is 5 seconds
> 
> Dan, since we poll only every 15s and cpu info is 15s wouldn't it make
> sense to change the default for network monitoring to 15s as well?
> it's 2 libvirt rounds trip for nothing really. Or does it serve some
> other purpose?

I see no motivation for Vdsm to poll libvirt faster than Engine polls
Vdsm.

Maybe Federico, who's improved scalability back in
https://bugzilla.redhat.com/show_bug.cgi?id=661321 [vdsm] [scale] vdsm CPU consumption goes between 180-400 when running 100 vms
remembers a reason.

I'm for changing the default to 15.