Re: [Xen-devel] [PATCH 2/7] xen/tools: credit2: soft-affinity awareness in runq_tickle()

[Anshul Makkar <anshul.makkar@xxxxxxxxxx>]

On 16/06/2017 15:13, Dario Faggioli wrote:
> Soft-affinity support is usually implemented by means
> of a two step "balancing loop", where:
> - during the first step, we consider soft-affinity
>   (if the vcpu has one);
> - during the second (if we get to it), we consider
>   hard-affinity.
>
> In runq_tickle(), we need to do that for checking
> whether we can execute the waking vCPU on an pCPU
> that is idle. In fact, we want to be sure that, if
> there is an idle pCPU in the vCPU's soft affinity,
> we'll use it.
>
> If there are no such idle pCPUs, though, and we
> have to check non-idle ones, we can avoid the loop
> and to both hard and soft-affinity in one pass.
>
> In fact, we can we scan runqueue and compute a
> "score" for each vCPU which is running on each pCPU.
> The idea is, since we may have to preempt someone:
> - try to make sure that the waking vCPU will run
>   inside its soft-affinity,
> - try to preempt someone that is running outside
>   of its own soft-affinity.
>
> The value of the score is added to a trace record,
> so xenalyze's code and tools/xentrace/formats are
> updated accordingly.
>
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
> Cc: Anshul Makkar <anshul.makkar@xxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
reviewed. Looks good.

Anshul



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