Re: [PATCH] sched/schedutil : optimize utilization scaling for guest kernel

From: Peter Zijlstra
Date: Wed Aug 29 2018 - 08:45:13 EST

On Wed, Aug 29, 2018 at 10:51:42AM +0200, Vincent Guittot wrote:
> Scaling the utilization of CPUs with irq util_avg in schedutil doesn't give
> any benefit and just waste CPU cycles when irq time is not accounted but
> only steal time.
> Add an internal _scale_irq_capacity() for scale_rt_capacity but scale
> cpu utilization in schedutil only if we are accounting irq time.

This makes a mess of things; also it doesn't really do what it says.

Even if we have CONFIG_IRQ_TIME_ACCOUNTING, that doesn't mean we do it,
just that it is capable.