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Wysocki" , Viresh Kumar , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Loehle , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] cpufreq: schedutil: Don't ignore limit changes when util is unchanged Date: Wed, 9 Apr 2025 19:44:37 -0700 Message-ID: <20250410024439.20859-1-sultan@kerneltoast.com> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Sultan Alsawaf When utilization is unchanged, a policy limits update is ignored unless CPUFREQ_NEED_UPDATE_LIMITS is set. This occurs because limits_changed depends on the old broken behavior of need_freq_update to trigger a call into cpufreq_driver_resolve_freq() to evaluate the changed policy limits. After fixing need_freq_update, limit changes are ignored without CPUFREQ_NEED_UPDATE_LIMITS, at least until utilization changes enough to make map_util_freq() return something different. Fix the ignored limit changes by preserving the value of limits_changed until get_next_freq() is called, so limits_changed can trigger a call to cpufreq_driver_resolve_freq(). Reported-and-tested-by: Stephan Gerhold Link: https://lore.kernel.org/lkml/Z_Tlc6Qs-tYpxWYb@linaro.org Fixes: 8e461a1cb43d6 ("cpufreq: schedutil: Fix superfluous updates caused by need_freq_update") Signed-off-by: Sultan Alsawaf --- kernel/sched/cpufreq_schedutil.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 1a19d69b91ed3..f37b999854d52 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -82,7 +82,6 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time) return false; if (unlikely(sg_policy->limits_changed)) { - sg_policy->limits_changed = false; sg_policy->need_freq_update = cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS); return true; } @@ -171,9 +170,11 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy, freq = get_capacity_ref_freq(policy); freq = map_util_freq(util, freq, max); - if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update) + if (freq == sg_policy->cached_raw_freq && !sg_policy->limits_changed && + !sg_policy->need_freq_update) return sg_policy->next_freq; + sg_policy->limits_changed = false; sg_policy->cached_raw_freq = freq; return cpufreq_driver_resolve_freq(policy, freq); }