Re: [Xen-devel] [PATCH 19/19] xen: credit2: use cpumask_first instead of cpumask_any when choosing cpu

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 18/06/16 00:13, Dario Faggioli wrote:
> because it is cheaper, and there is no much point in
> randomizing which cpu gets selected anyway, as such
> choice will be overridden shortly after, in runq_tickle().
> 
> If we really feel the need (e.g., we prove it worth with
> benchmarking), we can record the last cpu which was used
> by csched2_cpu_pick() and migrate() in a per-runq variable,
> and then use cpumask_cycle()... but this really does not
> look necessary.

Isn't this backwards?  Surely you should demonstrate that this change is
beneficial before proposing it?

I don't think any performance related change should be accepted without
experimental evidence that it makes something better, especially if it
looks like it might have negative consequences (e.g., by favouring low
cpus).

David


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel