On Sat, Aug 16, 2025 at 02:16:18AM +0800, Wentao Guan wrote:
From: Vincent Guittot vincent.guittot@linaro.org
Linus reported a ~50% performance regression on single-threaded workloads on his AMD Ryzen system, and bisected it to:
9c0b4bb7f630 ("sched/cpufreq: Rework schedutil governor performance estimation")
When frequency invariance is not enabled, get_capacity_ref_freq(policy) is supposed to return the current frequency and the performance margin applied by map_util_perf(), enabling the utilization to go above the maximum compute capacity and to select a higher frequency than the current one.
After the changes in 9c0b4bb7f630, the performance margin was applied earlier in the path to take into account utilization clampings and we couldn't get a utilization higher than the maximum compute capacity, and the CPU remained 'stuck' at lower frequencies.
To fix this, we must use a frequency above the current frequency to get a chance to select a higher OPP when the current one becomes fully used. Apply the same margin and return a frequency 25% higher than the current one in order to switch to the next OPP before we fully use the CPU at the current one.
[ mingo: Clarified the changelog. ]
Fixes: 9c0b4bb7f630 ("sched/cpufreq: Rework schedutil governor performance estimation") Reported-by: Linus Torvalds torvalds@linux-foundation.org Bisected-by: Linus Torvalds torvalds@linux-foundation.org Reported-by: Wyes Karny wkarny@gmail.com Signed-off-by: Vincent Guittot vincent.guittot@linaro.org Signed-off-by: Ingo Molnar mingo@kernel.org Tested-by: Wyes Karny wkarny@gmail.com Link: https://lore.kernel.org/r/20240114183600.135316-1-vincent.guittot@linaro.org (cherry picked from commit e37617c8e53a1f7fcba6d5e1041f4fd8a2425c27)
kernel/sched/cpufreq_schedutil.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
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