linux-kernel - Re: [PATCH V3] acpi: Allow ignoring _OSC CPPC v2 bit via kernel parameter

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Date: Wed, 19 Jun 2024 20:05:25 -0500
From: Aaron Rainbolt <arainbolt@...cus.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Mario Limonciello <mario.limonciello@....com>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	lenb@...nel.org, mmikowski@...cus.org, Perry.Yuan@....com,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH V3] acpi: Allow ignoring _OSC CPPC v2 bit via kernel
 parameter

OK, we have done thorough benchmarking of the two patches. In summary,
they both seem to provide exactly the same performance improvements.
My initial worry that Rafael's patch didn't deliver the same performance
improvements was unfounded.

The following are the single-core and multi-core scores from running
Geekbench 5 multiple times on a Carbon Systems Iridium 16 system. The
first batch of tests was done with an Ubuntu kernel built with with my V3
proposed patch, while the second batch was done with a kernel build with
Rafael's proposed patch.

Links to the Geekbench 5 reports can be shared if needed.

_OSC CPPC bit ignore patch (written by Aaron Rainbolt):
Kernel parameter 'ignore_osc_cppc_bit' set in
'/etc/default/grub.d/kfocus.cfg'.
'/sys/devices/system/cpu/cpu*/acpi_cppc' and
'/proc/sys/kernel/sched_itmt_enabled' both present

| Run | Single | Multi  |
| --- | ------ | ------ |
|  01 |   1874 |  10475 |
|  02 |   1831 |  10132 |
|  03 |   1858 |  10348 |
|  04 |   1848 |  10370 |
|  05 |   1831 |  10413 |
| --- | ------ | ------ |
| AVG |   1848 |  10348 |

intel_pstate CPPC override patch (written by Rafael Wysocki):
No special kernel parameters set.
'/sys/devices/system/cpu/cpu*/acpi_cppc' ABSENT,
'/proc/sys/kernel/sched_itmt_enabled' present

| Run | Single | Multi  |
| --- | ------ | ------ |
|  01 |   1820 |  10310 |
|  02 |   1870 |  10303 |
|  03 |   1867 |  10420 |
|  04 |   1844 |  10283 |
|  05 |   1835 |  10451 |
| --- | ------ | ------ |
| AVG |   1847 |  10353 |