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cpufreq: schedutil: Fix superfluous updates caused by need_freq_update

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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: 600f5badb7 ("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>
This commit is contained in:
Sultan Alsawaf (unemployed) 2024-12-11 17:57:32 -08:00 committed by Rafael J. Wysocki
parent de51589f9b
commit 8e461a1cb4
1 changed files with 2 additions and 2 deletions
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4
kernel/sched/cpufreq_schedutil.c
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@ -83,7 +83,7 @@ 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;
}
@ -96,7 +96,7 @@ 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;