Re: [PATCH v2 0/2] AMD Pstate driver fixes

From: Dhananjay Ugwekar
Date: Tue Jul 02 2024 - 04:25:13 EST

Forgot to mention the v2 changes,

v2 changes:
* Add reported-by tags (Gautham)
* Modify patch 2 to use amd_pstate_update_perf (Mario)
* Modify commit name for patch 1 (Gautham)
* Modify commit message for patch 2, from scaling_min/max_freq to
just scaling_max_freq, as scaling_min_freq still needs some debugging
to work correctly with active mode.

Regards,
Dhananjay

On 7/2/2024 1:44 PM, Dhananjay Ugwekar wrote:
> 1. Handle the nominal freq units inconsistency in amd-pstate-ut, which was
> leading to the below error on inserting the amd-pstate-ut module.
>
> [ 4982.498864] amd_pstate_ut: 1 amd_pstate_ut_acpi_cpc_valid success!
> [ 4982.498873] amd_pstate_ut: 2 amd_pstate_ut_check_enabled success!
> [ 4982.509151] amd_pstate_ut: 3 amd_pstate_ut_check_perf success!
> [ 4982.509155] amd_pstate_ut: amd_pstate_ut_check_freq cpu0 max=3709000 >= nominal=2401 > lowest_nonlinear=1903000 > min=400000 > 0, the formula is incorrect!
> [ 4982.509157] amd_pstate_ut: 4 amd_pstate_ut_check_freq fail!
>
> 2. Setting the scaling_max_freq on shared memory CPPC systems was
> broken in amd-pstate-epp driver(amd_pstate=active mode). The
> scaling_max_freq value was not being propagated to the shared memory area,
> so the frequency capping was not being honored.
>
> Tested on a AMD Zen3 Milan machine(shared memory CPPC):
>
> stress-ng is running on the system to keep the CPU utilization at 100%
> to test the scaling_max_freq capping.
>
> Before the patch:
> We can see below, setting the scaling_max_freq is not taking effect.
>
> linux/tools/power/x86/turbostat# ./turbostat --Summary
> turbostat version 2023.11.07 - Len Brown <lenb@xxxxxxxxxx>
> [Snip]
> cpu0: cpufreq driver: amd-pstate-epp
> cpu0: cpufreq governor: performance
> [Snip]
> Avg_MHz Busy% Bzy_MHz TSC_MHz IPC IRQ POLL C1 C2 POLL% C1% C2% CorWatt PkgWatt
> 2620 100.00 2620 2026 0.80 164935 0 0 0 0.00 0.00 0.00 176.07 249.18
> 2580 100.00 2580 1995 0.80 162208 0 0 0 0.00 0.00 0.00 173.27 245.37
> 2584 100.00 2584 1998 0.79 162379 0 0 0 0.00 0.00 0.00 173.42 245.68
> 2577 100.00 2577 1996 0.79 162146 0 0 0 0.00 0.00 0.00 173.15 245.41
> 2578 100.00 2578 1996 0.80 162025 0 0 0 0.00 0.00 0.00 173.07 245.46
> 2575 100.00 2575 1996 0.80 162115 0 0 0 0.00 0.00 0.00 172.96 245.41
> 2576 100.00 2576 1996 0.79 161998 0 0 0 0.00 0.00 0.00 172.87 245.32
> linux/tools/power/x86/turbostat# echo 2000000 | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq
> 2000000
> linux/tools/power/x86/turbostat# cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq | uniq
> 2000000
> linux/tools/power/x86/turbostat# ./turbostat --Summary
> turbostat version 2023.11.07 - Len Brown <lenb@xxxxxxxxxx>
> [Snip]
> cpu0: cpufreq driver: amd-pstate-epp
> cpu0: cpufreq governor: performance
> [Snip]
> Avg_MHz Busy% Bzy_MHz TSC_MHz IPC IRQ POLL C1 C2 POLL% C1% C2% CorWatt PkgWatt
> 2620 100.00 2620 2038 0.79 166103 0 0 2 0.00 0.00 0.00 175.44 250.96
> 2566 100.00 2566 1996 0.79 162038 0 0 0 0.00 0.00 0.00 171.79 245.23
> 2566 100.00 2566 1996 0.79 162289 0 0 0 0.00 0.00 0.00 171.76 245.59
> 2571 100.00 2571 1996 0.80 162034 0 0 0 0.00 0.00 0.00 171.69 245.44
> 2566 100.00 2566 1996 0.79 162179 0 0 0 0.00 0.00 0.00 171.62 245.41
> 2567 100.00 2567 1996 0.79 162028 0 0 0 0.00 0.00 0.00 171.57 245.46
> 2567 100.00 2567 1996 0.80 162037 0 0 0 0.00 0.00 0.00 171.53 245.41
>
> After applying the patch:
> On setting scaling_max_freq at 2GHz, the CPU frequency gets capped at 2GHz.
>
> linux/tools/power/x86/turbostat# ./turbostat --Summary
> turbostat version 2023.11.07 - Len Brown <lenb@xxxxxxxxxx>
> [Snip]
> cpu0: cpufreq driver: amd-pstate-epp
> cpu0: cpufreq governor: performance
> [Snip]
> Avg_MHz Busy% Bzy_MHz TSC_MHz IPC IRQ POLL C1 C2 POLL% C1% C2% CorWatt PkgWatt
> 2551 100.00 2551 1956 0.80 165998 0 0 0 0.00 0.00 0.00 171.34 231.22
> 2713 100.00 2713 2078 0.79 175801 0 0 0 0.00 0.00 0.00 181.92 266.13
> 2594 100.00 2594 1991 0.79 162183 0 0 1 0.00 0.00 0.00 173.99 244.50
> 2606 100.00 2606 2003 0.79 162632 0 0 0 0.00 0.00 0.00 174.81 246.51
> 2599 100.00 2599 1996 0.79 162168 0 0 0 0.00 0.00 0.00 174.05 245.46
> linux/tools/power/x86/turbostat# echo 2000000 | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq
> 2000000
> linux/tools/power/x86/turbostat# cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq | uniq
> 2000000
> linux/tools/power/x86/turbostat# ./turbostat --Summary
> turbostat version 2023.11.07 - Len Brown <lenb@xxxxxxxxxx>
> [Snip]
> cpu0: cpufreq driver: amd-pstate-epp
> cpu0: cpufreq governor: performance
> [Snip]
> Avg_MHz Busy% Bzy_MHz TSC_MHz IPC IRQ POLL C1 C2 POLL% C1% C2% CorWatt PkgWatt
> 2010 100.00 2010 2030 0.80 165565 0 0 0 0.00 0.00 0.00 101.22 173.52
> 1975 100.00 1975 1995 0.80 162042 0 0 0 0.00 0.00 0.00 99.03 169.88
> 1977 100.00 1977 1998 0.80 162559 0 0 0 0.00 0.00 0.00 99.16 170.20
> 1976 100.00 1976 1996 0.80 162243 0 0 0 0.00 0.00 0.00 99.09 170.08
> 1976 100.00 1976 1996 0.80 162490 0 0 0 0.00 0.00 0.00 99.17 170.16
> 1976 100.00 1976 1996 0.80 162056 0 0 0 0.00 0.00 0.00 99.11 170.17
>
> Dhananjay Ugwekar (2):
> cpufreq/amd-pstate-ut: Convert nominal_freq to khz during comparisons
> cpufreq/amd-pstate: Fix the scaling_max_freq setting on shared memory
> CPPC systems
>
> drivers/cpufreq/amd-pstate-ut.c | 12 +++++----
> drivers/cpufreq/amd-pstate.c | 43 ++++++++++++++++++---------------
> 2 files changed, 30 insertions(+), 25 deletions(-)
>