diff mbox

[V2] cpufreq: schedutil: Redefine the rate_limit_us tunable

Message ID 250f484b4fec4922601f18e719f587aa40c8b220.1487651965.git.viresh.kumar@linaro.org
State Accepted
Commit 994a8f2514e91c16616c4a1b53e9eb2b24de97b7
Headers show

Commit Message

Viresh Kumar Feb. 21, 2017, 4:45 a.m. UTC 
The rate_limit_us tunable is intended to reduce the possible overhead
from running the schedutil governor.  However, that overhead can be
divided into two separate parts: the governor computations and the
invocation of the scaling driver to set the CPU frequency.  The latter
is where the real overhead comes from.  The former is much less
expensive in terms of execution time and running it every time the
governor callback is invoked by the scheduler, after rate_limit_us
interval has passed since the last frequency update, would not be a
problem.

For this reason, redefine the rate_limit_us tunable so that it means the
minimum time that has to pass between two consecutive invocations of the
scaling driver by the schedutil governor (to set the CPU frequency).

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

---
V1->V2: Update $subject and commit log (Rafael)

 kernel/sched/cpufreq_schedutil.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.7.1.410.g6faf27b

Comments

Viresh Kumar Feb. 24, 2017, 2:29 a.m. UTC | #1 
On 24-02-17, 00:36, Rafael J. Wysocki wrote:
> I'd prefer this to spend some time in linux-next before it goes into

> the mainline, so I will queue it up for 4.12 if no one objects by the

> end of the next week.


Sure. Thanks.

-- 
viresh
diff mbox

Patch

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index fd4659313640..306d97e7b57c 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -92,14 +92,13 @@  static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
 {
 	struct cpufreq_policy *policy = sg_policy->policy;
 
-	sg_policy->last_freq_update_time = time;
-
 	if (policy->fast_switch_enabled) {
 		if (sg_policy->next_freq == next_freq) {
 			trace_cpu_frequency(policy->cur, smp_processor_id());
 			return;
 		}
 		sg_policy->next_freq = next_freq;
+		sg_policy->last_freq_update_time = time;
 		next_freq = cpufreq_driver_fast_switch(policy, next_freq);
 		if (next_freq == CPUFREQ_ENTRY_INVALID)
 			return;
@@ -108,6 +107,7 @@  static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
 		trace_cpu_frequency(next_freq, smp_processor_id());
 	} else if (sg_policy->next_freq != next_freq) {
 		sg_policy->next_freq = next_freq;
+		sg_policy->last_freq_update_time = time;
 		sg_policy->work_in_progress = true;
 		irq_work_queue(&sg_policy->irq_work);
 	}