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

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Message-ID: <CAJvTdK=wafegpUB-KD=P9KazWngMNQb_rcbwQX_DDwPBtZ9W7w@mail.gmail.com>
Date: Wed, 31 Jul 2024 12:28:29 -0400
From: Len Brown <lenb@...nel.org>
To: Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, "Zhang, Rui" <rui.zhang@...el.com>, 
	"jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>, 
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, 
	"artem.bityutskiy@...ux.intel.com" <artem.bityutskiy@...ux.intel.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH] intel_idle: Add Jasper Lake and Elkhart Lake support

On Wed, Jul 31, 2024 at 2:18 AM Kai-Heng Feng
<kai.heng.feng@...onical.com> 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?

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?

> Can we use that for EHL and JSL?

Yes.

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

-- 
Len Brown, Intel