Re: hotplug support for arch/arc/plat-eznps platform

From: Peter Zijlstra
Date: Mon Aug 07 2017 - 04:34:12 EST

On Sun, Aug 06, 2017 at 05:53:37AM +0000, Ofer Levi(SW) wrote:
> I'm adding hot-plug support for the above arch and ran into performance issue with execution of
> partition_sched_domains () - About 0.5 sec per cpu, which is unacceptable with the arch supported 4k cpus.
> To my limited understanding, on the plat-eznps arch, where each cpu is always running a single threaded process in
> isolation mode, the above call is not necessary,
> Can you please confirm (or reject) my understanding? If I'm wrong short explanation will be appreciated.
> If I'm correct, I will be grateful if you can point me to how to skip this call in a way acceptable by community.

You've failed to explain why you think hotplug should be a performance
critical path.

I'm also not seeing how it would be different from boot; you'd be
looking at a similar cost for SMP bringup.