[AMD Official Use Only - AMD Internal Distribution Only]
-----Original Message----- From: Nabil S. Alramli dev@nalramli.com Sent: Friday, October 25, 2024 9:05 AM To: stable@vger.kernel.org Cc: nalramli@fastly.com; jdamato@fastly.com; khubert@fastly.com; Yuan, Perry Perry.Yuan@amd.com; Meng, Li (Jassmine) Li.Meng@amd.com; Huang, Ray Ray.Huang@amd.com; rafael@kernel.org; viresh.kumar@linaro.org; linux- pm@vger.kernel.org; linux-kernel@vger.kernel.org; Nabil S. Alramli dev@nalramli.com Subject: [RFC PATCH 6.1.y 0/1] cpufreq: amd-pstate: Enable CPU boost in passive and guided modes
Greetings,
This is a RFC for a maintenance patch to an issue in the amd_pstate driver where CPU frequency cannot be boosted in passive or guided modes. Without this patch, AMD machines using stable kernels are unable to get their CPU frequency boosted, which is a significant performance issue.
For example, on a host that has AMD EPYC 7662 64-Core processor without this patch running at full CPU load:
$ for i in $(cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq); \ do ni=$(echo "scale=1; $i/1000000" | bc -l); echo "$ni GHz"; done | \ sort | uniq -c
128 2.0 GHzAnd with this patch:
$ for i in $(cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq); \ do ni=$(echo "scale=1; $i/1000000" | bc -l); echo "$ni GHz"; done | \ sort | uniq -c
128 3.3 GHzI am not sure what the correct process is for submitting patches which affect only stable trees but not the current code base, and do not apply to the current tree. As such, I am submitting this directly to stable@, but please let me know if I should be submitting this elsewhere.
The issue was introduced in v6.1 via commit bedadcfb011f ("cpufreq: amd-pstate: Fix initial highest_perf value"), and exists in stable kernels up until v6.6.51.
In v6.6.51, a large change, commit 1ec40a175a48 ("cpufreq: amd-pstate: Enable amd-pstate preferred core support"), was introduced which significantly refactored the code. This commit cannot be ported back on its own, and would require reviewing and cherry picking at least a few dozen of commits in cpufreq, amd-pstate, ACPI, CPPC.
This means kernels v6.1 up until v6.6.51 are affected by this significant performance issue, and cannot be easily remediated.
Thank you for your attention and I look forward to your response in regards to what the best way to proceed is for getting this important performance fix merged.
Best Regards,
Nabil S. Alramli (1): cpufreq: amd-pstate: Enable CPU boost in passive and guided modes
drivers/cpufreq/amd-pstate.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
-- 2.35.1
Add Mario and Gautham for any help.
Perry.