[PATCH v6 0/6] amd_pstate: Add guided autonomous mode support

Wyes Karny
2023-02-06T17:22:31Z

From ACPI spec[1] below 3 modes for CPPC can be defined:
1. Non autonomous: OS scaling governor specifies operating frequency/
performance level through `Desired Performance` register and platform
follows that.
2. Guided autonomous: OS scaling governor specifies min and max
frequencies/ performance levels through `Minimum Performance` and
`Maximum Performance` register, and platform can autonomously select an
operating frequency in this range.
3. Fully autonomous: OS only hints (via EPP) to platform for the required
energy performance preference for the workload and platform autonomously
scales the frequency.

Currently (1) is supported by amd_pstate as passive mode, and (3) is
implemented by EPP support[2]. This change is to support (2).

In guided autonomous mode the min_perf is based on the input from the
scaling governor. For example, in case of schedutil this value depends
on the current utilization. And max_perf is set to max capacity.

To activate guided auto mode ``amd_pstate=guided`` command line
parameter has to be passed in the kernel.

Below are the results (normalized) of benchmarks with this patch:
System: Genoa 96C 192T
Kernel: 6.2.0-rc2 + EPP v12 + patch
Scaling governor: schedutil

================ dbench comparisons ================
dbench result comparison:
Here results are throughput (MB/s)
Clients: acpi-cpufreq amd_pst+passive amd_pst+guided
1 1.00 (0.00 pct) 1.01 (1.00 pct) 1.02 (2.00 pct)
2 1.07 (0.00 pct) 1.06 (-0.93 pct) 1.07 (0.00 pct)
4 1.68 (0.00 pct) 1.70 (1.19 pct) 1.72 (2.38 pct)
8 2.61 (0.00 pct) 2.68 (2.68 pct) 2.76 (5.74 pct)
16 4.16 (0.00 pct) 4.24 (1.92 pct) 4.53 (8.89 pct)
32 5.98 (0.00 pct) 6.17 (3.17 pct) 7.30 (22.07 pct)
64 8.67 (0.00 pct) 8.99 (3.69 pct) 10.71 (23.52 pct)
128 11.98 (0.00 pct) 12.52 (4.50 pct) 14.67 (22.45 pct)
256 15.73 (0.00 pct) 16.13 (2.54 pct) 17.81 (13.22 pct)
512 15.77 (0.00 pct) 16.32 (3.48 pct) 16.39 (3.93 pct)
dbench power comparison:
Clients: acpi-cpufreq amd_pst+passive amd_pst+guided
1 1.00 (0.00 pct) 1.00 (0.00 pct) 1.04 (4.00 pct)
2 0.99 (0.00 pct) 0.97 (-2.02 pct) 1.02 (3.03 pct)
4 0.98 (0.00 pct) 0.98 (0.00 pct) 1.02 (4.08 pct)
8 0.98 (0.00 pct) 0.99 (1.02 pct) 1.02 (4.08 pct)
16 0.99 (0.00 pct) 1.00 (1.01 pct) 1.04 (5.05 pct)
32 1.02 (0.00 pct) 1.02 (0.00 pct) 1.07 (4.90 pct)
64 1.05 (0.00 pct) 1.05 (0.00 pct) 1.11 (5.71 pct)
128 1.08 (0.00 pct) 1.08 (0.00 pct) 1.15 (6.48 pct)
256 1.12 (0.00 pct) 1.12 (0.00 pct) 1.20 (7.14 pct)
512 1.18 (0.00 pct) 1.17 (-0.84 pct) 1.26 (6.77 pct)

================ git-source comparisons ================
git-source result comparison:
Here results are throughput (compilations per 1000 sec)
Threads: acpi-cpufreq amd_pst+passive amd_pst+guided
192 1.00 (0.00 pct) 0.93 (-7.00 pct) 1.00 (0.00 pct)
git-source power comparison:
Threads: acpi-cpufreq amd_pst+passive amd_pst+guided
192 1.00 (0.00 pct) 1.00 (0.00 pct) 0.96 (-4.00 pct)

================ kernbench comparisons ================
kernbench result comparison:
Here results are throughput (compilations per 1000 sec)
Load: acpi-cpufreq amd_pst+passive amd_pst+guided
32 1.00 (0.00 pct) 1.01 (1.00 pct) 1.02 (2.00 pct)
48 1.26 (0.00 pct) 1.28 (1.58 pct) 1.25 (-0.79 pct)
64 1.39 (0.00 pct) 1.47 (5.75 pct) 1.43 (2.87 pct)
96 1.48 (0.00 pct) 1.50 (1.35 pct) 1.49 (0.67 pct)
128 1.29 (0.00 pct) 1.32 (2.32 pct) 1.33 (3.10 pct)
192 1.17 (0.00 pct) 1.20 (2.56 pct) 1.21 (3.41 pct)
256 1.17 (0.00 pct) 1.18 (0.85 pct) 1.20 (2.56 pct)
384 1.16 (0.00 pct) 1.17 (0.86 pct) 1.21 (4.31 pct)
kernbench power comparison:
Clients: acpi-cpufreq amd_pst+passive amd_pst+guided
32 1.00 (0.00 pct) 0.97 (-3.00 pct) 1.00 (0.00 pct)
48 0.87 (0.00 pct) 0.81 (-6.89 pct) 0.88 (1.14 pct)
64 0.81 (0.00 pct) 0.73 (-9.87 pct) 0.77 (-4.93 pct)
96 0.75 (0.00 pct) 0.74 (-1.33 pct) 0.75 (0.00 pct)
128 0.83 (0.00 pct) 0.79 (-4.81 pct) 0.83 (0.00 pct)
192 0.92 (0.00 pct) 0.88 (-4.34 pct) 0.92 (0.00 pct)
256 0.92 (0.00 pct) 0.88 (-4.34 pct) 0.92 (0.00 pct)
384 0.92 (0.00 pct) 0.88 (-4.34 pct) 0.92 (0.00 pct)

================ tbench comparisons ================
tbench result comparison:
Here results are throughput (MB/s)
Clients: acpi-cpufreq amd_pst+passive amd_pst+guided
1 1.00 (0.00 pct) 0.70 (-30.00 pct) 1.37 (37.00 pct)
2 2.64 (0.00 pct) 1.39 (-47.34 pct) 2.70 (2.27 pct)
4 4.89 (0.00 pct) 2.75 (-43.76 pct) 5.28 (7.97 pct)
8 9.46 (0.00 pct) 5.42 (-42.70 pct) 10.22 (8.03 pct)
16 19.05 (0.00 pct) 10.42 (-45.30 pct) 19.94 (4.67 pct)
32 37.50 (0.00 pct) 20.23 (-46.05 pct) 36.87 (-1.68 pct)
64 61.24 (0.00 pct) 43.08 (-29.65 pct) 62.96 (2.80 pct)
128 67.16 (0.00 pct) 69.08 (2.85 pct) 67.34 (0.26 pct)
256 154.59 (0.00 pct) 162.33 (5.00 pct) 156.78 (1.41 pct)
512 154.02 (0.00 pct) 156.74 (1.76 pct) 153.48 (-0.35 pct)
tbench power comparison:
Clients: acpi-cpufreq amd_pst+passive amd_pst+guided
1 1.00 (0.00 pct) 0.97 (-3.00 pct) 1.08 (8.00 pct)
2 1.04 (0.00 pct) 0.97 (-6.73 pct) 1.11 (6.73 pct)
4 1.12 (0.00 pct) 0.99 (-11.60 pct) 1.18 (5.35 pct)
8 1.25 (0.00 pct) 1.04 (-16.80 pct) 1.31 (4.80 pct)
16 1.53 (0.00 pct) 1.13 (-26.14 pct) 1.58 (3.26 pct)
32 2.01 (0.00 pct) 1.36 (-32.33 pct) 2.03 (0.99 pct)
64 2.58 (0.00 pct) 2.14 (-17.05 pct) 2.61 (1.16 pct)
128 2.80 (0.00 pct) 2.81 (0.35 pct) 2.81 (0.35 pct)
256 3.39 (0.00 pct) 3.43 (1.17 pct) 3.42 (0.88 pct)
512 3.44 (0.00 pct) 3.44 (0.00 pct) 3.44 (0.00 pct)

Note: this series is based on top of EPP v12 [3] series

Change log:

v5 -> v6
- Don't return -EBUSY when changing to same mode

v4 -> v5:
- Rebased on top of EPP v12 series
- Addressed comments form Mario regarding documentation
- Picked up RB flags from Mario and Bagas Sanjaya

v3 -> v4:
- Fixed active mode low frequency issue reported by Peter Jung and Tor Vic
- Documentation modification suggested by Bagas Sanjaya

v2 -> v3:
- Addressed review comments form Mario.
- Picked up RB tag from Mario.
- Rebase on top of EPP v11 [3].

v1 -> v2:
- Fix issue with shared mem systems.
- Rebase on top of EPP series.

[1]: https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf
[2]: https://lore.kernel.org/lkml/20221110175847.3098728-1-Perry.Yuan@amd.com/
[3]: https://lore.kernel.org/linux-pm/20230131090016.3970625-1-perry.yuan@amd.com/

Wyes Karny (6):
acpi: cppc: Add min and max perf reg writing support
acpi: cppc: Add auto select register read/write support
cpufreq: amd_pstate: Add guided autonomous mode
Documentation: amd_pstate: Move amd_pstate param to alphabetical order
cpufreq: amd_pstate: Add guided mode control support via sysfs
Documentation: amd_pstate: Update amd_pstate status sysfs for guided

.../admin-guide/kernel-parameters.txt | 41 ++--
Documentation/admin-guide/pm/amd-pstate.rst | 31 ++-
drivers/acpi/cppc_acpi.c | 121 +++++++++++-
drivers/cpufreq/amd-pstate.c | 183 +++++++++++++-----
include/acpi/cppc_acpi.h | 11 ++
include/linux/amd-pstate.h | 2 +
6 files changed, 308 insertions(+), 81 deletions(-)

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2.34.1