Re: [Xen-devel] [PATCH v2 7/7] xen: credit2: avoid cpumask_any() in pick_cpu().

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 06/04/17 09:17, Dario Faggioli wrote:
> cpumask_any() is costly (because of the randomization).
> And since it does not really matter which exact CPU is
> selected within a runqueue, as that will be overridden
> shortly after, in runq_tickle(), spending too much time
> and achieving true randomization is pretty pointless.
> 
> As the picked CPU, however, would be used as an hint,
> within runq_tickle(), don't give up on it entirely,
> and let's make sure we don't always return the same
> CPU, or favour lower or higher ID CPUs.
> 
> To achieve that, let's record and remember, for each
> runqueue, what CPU we picked for last, and start from
> that the following time.
> 
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>


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