Re: Load calculation refresh in credit2 (was in Re: Questions about the use of idle_vcpu[])

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Mon, 2016-01-18 at 14:12 +0000, George Dunlap wrote:
> [Changing the title to align with the current topic]
> 
> Load balancing only happens on a reset event; and the frequency of
> reset
> events will be CREDIT_INIT / (% utilization); so for a system at 1%
> utilization that would be once every second.  Is that the kind of
> number
> you were seeing?  Or were you actually seeing idle runqueues not
> having
> anything pushed to them *during* a balance for some reason?
> 
As I said, I need to recheck... but yes, this could be the cause of my
"issue".

In fact, since I was reading the load from the toolstack (that was one
of the purposes of the whole thing), it's quite likely that I was
seeing non-updated values because the load balance hadn't run since a
while.

I'll keep this in mind when revisiting that work, and try to cook a
patch that avoid setting the timer when the idle vcpu is returned, and
see how it goes.

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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