5.15-stable review patch. If anyone has any objections, please let me know.
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From: Sultan Alsawaf (unemployed) sultan@kerneltoast.com
[ Upstream commit 8e461a1cb43d69d2fc8a97e61916dce571e6bb31 ]
A redundant frequency update is only truly needed when there is a policy limits change with a driver that specifies CPUFREQ_NEED_UPDATE_LIMITS.
In spite of that, drivers specifying CPUFREQ_NEED_UPDATE_LIMITS receive a frequency update _all the time_, not just for a policy limits change, because need_freq_update is never cleared.
Furthermore, ignore_dl_rate_limit()'s usage of need_freq_update also leads to a redundant frequency update, regardless of whether or not the driver specifies CPUFREQ_NEED_UPDATE_LIMITS, when the next chosen frequency is the same as the current one.
Fix the superfluous updates by only honoring CPUFREQ_NEED_UPDATE_LIMITS when there's a policy limits change, and clearing need_freq_update when a requisite redundant update occurs.
This is neatly achieved by moving up the CPUFREQ_NEED_UPDATE_LIMITS test and instead setting need_freq_update to false in sugov_update_next_freq().
Fixes: 600f5badb78c ("cpufreq: schedutil: Don't skip freq update when limits change") Signed-off-by: Sultan Alsawaf (unemployed) sultan@kerneltoast.com Reviewed-by: Christian Loehle christian.loehle@arm.com Link: https://patch.msgid.link/20241212015734.41241-2-sultan@kerneltoast.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/cpufreq_schedutil.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 7f6bb37d3a2f7..e23a0fc96a7d2 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -91,7 +91,7 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
if (unlikely(sg_policy->limits_changed)) { sg_policy->limits_changed = false; - sg_policy->need_freq_update = true; + sg_policy->need_freq_update = cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS); return true; }
@@ -104,7 +104,7 @@ static bool sugov_update_next_freq(struct sugov_policy *sg_policy, u64 time, unsigned int next_freq) { if (sg_policy->need_freq_update) - sg_policy->need_freq_update = cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS); + sg_policy->need_freq_update = false; else if (sg_policy->next_freq == next_freq) return false;