[RFC PATCH v1 5/8] sched/cpufreq_schedutil: always consider all CPUs when deciding next freq

Juri Lelli
2017-07-05T09:00:44Z

No assumption can be made upon the rate at which frequency updates get
triggered, as there are scheduling policies (like SCHED_DEADLINE) which
don't trigger them so frequently.

Remove such assumption from the code, by always considering
SCHED_DEADLINE utilization signal as not stale.

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
Cc: Claudio Scordino <claudio@evidence.eu.com>
---
kernel/sched/cpufreq_schedutil.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index e835fa886225..066b876d81e7 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -267,17 +267,22 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
s64 delta_ns;

/*
- * If the CPU utilization was last updated before the previous
- * frequency update and the time elapsed between the last update
- * of the CPU utilization and the last frequency update is long
- * enough, don't take the CPU into account as it probably is
- * idle now (and clear iowait_boost for it).
+ * If the CFS CPU utilization was last updated before the
+ * previous frequency update and the time elapsed between the
+ * last update of the CPU utilization and the last frequency
+ * update is long enough, reset iowait_boost and util_cfs, as
+ * they are now probably stale. However, still consider the
+ * CPU contribution if it has some DEADLINE utilization
+ * (util_dl).
*/
delta_ns = time - j_sg_cpu->last_update;
if (delta_ns > TICK_NSEC) {
j_sg_cpu->iowait_boost = 0;
- continue;
+ j_sg_cpu->util_cfs = 0;
+ if (j_sg_cpu->util_dl == 0)
+ continue;
}
+
if (j_sg_cpu->flags & SCHED_CPUFREQ_RT)
return policy->cpuinfo.max_freq;

--
2.11.0