Re: [PATCH] intel_idle: add CPUIDLE_FLAG_IRQ_ENABLE to SPR C1 and C1E

[Artem Bityutskiy]

Hi Jon,

On Thu, 2022-06-30 at 15:43 -0400, Jon Kohler wrote:
> Add CPUIDLE_FLAG_IRQ_ENABLE to spr_cstates C1 and C1E, which will
> allow local IRQs to be enabled during fast idle transitions on SPR.

Did you have a chance to measure this? When I was doing this for ICX and CLX, I
was using cyclictest and wult for measuring IRQ latency.

I was planning to do this for SPR as well.

> Note: Enabling this for both C1 and C1E is slightly different than
> the approach for SKX/ICX, where CPUIDLE_FLAG_IRQ_ENABLE is only
> enabled on C1; however, given that SPR target/exit latency is 1/1
> for c1 and 2/4 for C1E, respectively, which is slower than C1
> for SKX, it seems prudent to now enable it on both states.

I was also going to measure this for C1E.

Could we please hold on this a bit - I'd like to measure this before we merge
it.

Artem.