[RFC PATCH] sched: Add scx_cpuperf_target in sched_cpu_util()

[Xuewen Yan]

Recently, while enabling sched-ext debugging, we observed abnormal behavior
in our thermal power_allocator’s temperature control.
Through debugging, we found that the CPU util was too low, causing
the CPU frequency to remain unrestricted.

This issue stems from the fact that in the sched_cpu_util() function,
when scx is enabled, cpu_util_cfs becomes zero. As a result,
the thermal subsystem perceives an extremely low CPU utilization,
which degrades the effectiveness of the power_allocator’s control.

To address this, we propose adding scx_cpuperf_target in the sched_cpu_util()
as a replacement for cpu_util_cfs, ensuring that the thermal subsystem receives
accurate load information and restores proper control behavior.

Reported-by: Di Shen <di.shen@xxxxxxxxxx>
Signed-off-by: Xuewen Yan <xuewen.yan@xxxxxxxxxx>
---
 kernel/sched/fair.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bf948db905ed..20adb6fede2a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8198,7 +8198,12 @@ unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
 
 unsigned long sched_cpu_util(int cpu)
 {
-	return effective_cpu_util(cpu, cpu_util_cfs(cpu), NULL, NULL);
+	unsigned long util = scx_cpuperf_target(cpu);
+
+	if (!scx_switched_all())
+		util += cpu_util_cfs(cpu);
+
+	return effective_cpu_util(cpu, util, NULL, NULL);
 }
 
 /*
-- 
2.25.1