Re: [PATCH] intel_idle: Add Jasper Lake and Elkhart Lake support

[Kai-Heng Feng]

On Thu, Aug 1, 2024 at 12:28 AM Len Brown <lenb@xxxxxxxxxx> wrote:
>
> On Wed, Jul 31, 2024 at 2:18 AM Kai-Heng Feng
> <kai.heng.feng@xxxxxxxxxxxxx> wrote:
> >
> > The crucial part to make the issue (i.e. slow ethernet) is
> > ".disable_promotion_to_c1e = true".
>
> Okay, so the problem statement is that on this machine with some
> ethernet controller and some workload,
> performance is better when you use just C1 and not C1E (or deeper) states.
>
> And so you want to have the option of accessing C1 without the overhead of C1E?

Yes, that's the case here.

>
> Presumably you don't care about the power savings of the deeper states,
> or you are using PM_QOS to avoid deep c-states at run time?

I tried to use cpu_latency_qos in the network driver's NAPI poll, but
only saw marginal improvement to around 830Mbps. Hitting the 940Mbps
is still the goal here.

>
> > Can we use that for EHL and JSL?
>
> Yes.

Is it plausible to disable C1E promotion while using ACPI idle driver?
Or provide a C-state table in intel_idle and update the states via
_CST?

>
> You may also have a BIOS option to achieve the same goal, depending on
> the platform.)

I am seeing three different platforms from different vendors hitting
the same issue, so it's better to disable C1e for these platforms.

Kai-Heng

>
> --
> Len Brown, Intel
>