From: Vincent Guittot <vincent.guittot@linaro.org> mainline inclusion from mainline-v6.8-rc1 commit e37617c8e53a1f7fcba6d5e1041f4fd8a2425c27 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IDC9YK Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commi... -------------------------------- 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 Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- kernel/sched/cpufreq_schedutil.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 2ec84ade9cac..61c3e0706f13 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -145,7 +145,11 @@ unsigned long get_capacity_ref_freq(struct cpufreq_policy *policy) if (arch_scale_freq_invariant()) return policy->cpuinfo.max_freq; - return policy->cur; + /* + * Apply a 25% margin so that we select a higher frequency than + * the current one before the CPU is fully busy: + */ + return policy->cur + (policy->cur >> 2); } /** -- 2.34.1