[PATCH 11/39] cpufreq_schedutil: Refactor sugov_cpu_is_busy()

Tejun Heo
2024-05-01T15:13:40Z

sugov_cpu_is_busy() is used to avoid decreasing performance level while the
CPU is busy and called by sugov_update_single_freq() and
sugov_update_single_perf(). Both callers repeat the same pattern to first
test for uclamp and then the business. Let's refactor so that the tests
aren't repeated.

The new helper is named sugov_hold_freq() and tests both the uclamp
exception and CPU business. No functional changes. This will make adding
more exception conditions easier.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
kernel/sched/cpufreq_schedutil.c | 38 +++++++++++++++-----------------
1 file changed, 18 insertions(+), 20 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index eece6244f9d2..972b7dd65af2 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -325,16 +325,27 @@ static unsigned long sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
}

#ifdef CONFIG_NO_HZ_COMMON
-static bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu)
+static bool sugov_hold_freq(struct sugov_cpu *sg_cpu)
{
- unsigned long idle_calls = tick_nohz_get_idle_calls_cpu(sg_cpu->cpu);
- bool ret = idle_calls == sg_cpu->saved_idle_calls;
+ unsigned long idle_calls;
+ bool ret;
+
+ /* if capped by uclamp_max, always update to be in compliance */
+ if (uclamp_rq_is_capped(cpu_rq(sg_cpu->cpu)))
+ return false;
+
+ /*
+ * Maintain the frequency if the CPU has not been idle recently, as
+ * reduction is likely to be premature.
+ */
+ idle_calls = tick_nohz_get_idle_calls_cpu(sg_cpu->cpu);
+ ret = idle_calls == sg_cpu->saved_idle_calls;

sg_cpu->saved_idle_calls = idle_calls;
return ret;
}
#else
-static inline bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu) { return false; }
+static inline bool sugov_hold_freq(struct sugov_cpu *sg_cpu) { return false; }
#endif /* CONFIG_NO_HZ_COMMON */

/*
@@ -382,14 +393,8 @@ static void sugov_update_single_freq(struct update_util_data *hook, u64 time,
return;

next_f = get_next_freq(sg_policy, sg_cpu->util, max_cap);
- /*
- * Do not reduce the frequency if the CPU has not been idle
- * recently, as the reduction is likely to be premature then.
- *
- * Except when the rq is capped by uclamp_max.
- */
- if (!uclamp_rq_is_capped(cpu_rq(sg_cpu->cpu)) &&
- sugov_cpu_is_busy(sg_cpu) && next_f < sg_policy->next_freq &&
+
+ if (sugov_hold_freq(sg_cpu) && next_f < sg_policy->next_freq &&
!sg_policy->need_freq_update) {
next_f = sg_policy->next_freq;

@@ -436,14 +441,7 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time,
if (!sugov_update_single_common(sg_cpu, time, max_cap, flags))
return;

- /*
- * Do not reduce the target performance level if the CPU has not been
- * idle recently, as the reduction is likely to be premature then.
- *
- * Except when the rq is capped by uclamp_max.
- */
- if (!uclamp_rq_is_capped(cpu_rq(sg_cpu->cpu)) &&
- sugov_cpu_is_busy(sg_cpu) && sg_cpu->util < prev_util)
+ if (sugov_hold_freq(sg_cpu) && sg_cpu->util < prev_util)
sg_cpu->util = prev_util;

cpufreq_driver_adjust_perf(sg_cpu->cpu, sg_cpu->bw_min,
--
2.44.0