Re: [for-4.8 PATCH] xen: credit2: make runqueues be per-socket by default.

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

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On Tue, 2016-11-29 at 11:14 +0000, Wei Liu wrote:
> On Tue, Nov 29, 2016 at 11:57:03AM +0100, Dario Faggioli wrote:
> Strictly speaking, this is not necessary for 4.8 because even though
> the
> default configuration is not optimal, there is a simple way to change
> it.
> 
Absolutely true.

> On the other hand, because credit2 is declared supported in this
> release, it is better to have a sensible default setting for credit2.
> 
Exactly.

> The risk is that changing the default value would cause osstest to
> discover bugs in the scheduler logic, hence blocking the release. But
> overall I think the chance is low, but Dario can you please state to
> what extend did you test this patch?
> 
I've tried to state that in the cover letter:
https://lists.xen.org/archives/html/xen-devel/2016-11/msg02616.html

In some more details, it is _months_ that I and Anshul run benchmarks
with Credit2 running in this configuration.

It's months that, all the time that I boot my test box, either to do
Credit2 related development and testing, or completely unrelated things
(e.g., recently, when testing the new Fedora 25 as HVM and PV guest), I
use Credit2 in this configuration.

George has done some runs of his schedbench suite with this
configuration (to compare Credit1 vs Credit2 per-core vs Credit2 per-
socket).

So, if you ask me "how much is this tested", my answer would be "really
really really a lot". :-)

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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