Re: [RFCv2 4/6] sched/fair: Define core capacity to limit task packing

Peter Zijlstra
2019-05-15T16:37:59Z

On Wed, May 15, 2019 at 07:23:20PM +0530, Parth Shah wrote:
> The task packing on a core needs to be bounded based on its capacity. This
> patch defines a new method which acts as a tipping point for task packing.
>
> The Core capacity is the method which limits task packing above certain
> point. In general, the capacity of a core is defined to be the aggregated
> sum of all the CPUs in the Core.
>
> Some architectures does not have core capacity linearly increasing with the
> number of threads( or CPUs) in the core. For such cases, architecture
> specific calculations needs to be done to find core capacity.
>
> The `arch_scale_core_capacity` is currently tuned for `powerpc` arch by
> scaling capacity w.r.t to the number of online SMT in the core.
>
> The patch provides default handler for other architecture by scaling core
> capacity w.r.t. to the capacity of all the threads in the core.
>
> ToDo: SMT mode is calculated each time a jitter task wakes up leading to
> redundant decision time which can be eliminated by keeping track of online
> CPUs during hotplug task.

Urgh, we just got rid of capacity for SMT. Also I don't think the above
clearly defines your metric.