Re: [PATCH 4/4] sched/fair: Use a recently used CPU as an idle candidate and the basis for SIS

[Peter Zijlstra]

On Fri, Feb 02, 2018 at 01:46:47PM +0100, Peter Zijlstra wrote:

> +static void __intel_pstate_hwp_set_desired(int val)
> +{
> +	u64 value;
> +
> +	value = rdmsrl(MSR_HWP_REQUEST);
> +	value &= ~GENMASK_ULL(23, 16);
> +	value |= (val & 0xff) << 16;
> +	wrmsrl(MSR_HWP_REQUEST, val);
> +}

Also, if we keep a software shadow of that MSR, we can avoid the
rdmsr, which might also help.