sched/cpufreq: Optimize cpufreq update kicker to avoid update multiple times

Sometimes delta_exec is 0 due to update_curr() is called multiple times,
this is captured by:

	u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start;

This patch optimizes the cpufreq update kicker by bailing out when nothing
changed, it will benefit the upcoming schedutil, since otherwise it will
(over)react to the special util/max combination.

Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1461316044-9520-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index affd97e..8f9b5af 100644 (file)
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -717,10 +717,6 @@ static void update_curr_dl(struct rq *rq)
        if (!dl_task(curr) || !on_dl_rq(dl_se))
                return;
 
-       /* Kick cpufreq (see the comment in linux/cpufreq.h). */
-       if (cpu_of(rq) == smp_processor_id())
-               cpufreq_trigger_update(rq_clock(rq));
-
        /*
         * Consumed budget is computed considering the time as
         * observed by schedulable tasks (excluding time spent
@@ -736,6 +732,10 @@ static void update_curr_dl(struct rq *rq)
                return;
        }
 
+       /* kick cpufreq (see the comment in linux/cpufreq.h). */
+       if (cpu_of(rq) == smp_processor_id())
+               cpufreq_trigger_update(rq_clock(rq));
+
        schedstat_set(curr->se.statistics.exec_max,
                      max(curr->se.statistics.exec_max, delta_exec));
 

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index c41ea7a..19e1306 100644 (file)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -953,14 +953,14 @@ static void update_curr_rt(struct rq *rq)
        if (curr->sched_class != &rt_sched_class)
                return;
 
-       /* Kick cpufreq (see the comment in linux/cpufreq.h). */
-       if (cpu_of(rq) == smp_processor_id())
-               cpufreq_trigger_update(rq_clock(rq));
-
        delta_exec = rq_clock_task(rq) - curr->se.exec_start;
        if (unlikely((s64)delta_exec <= 0))
                return;
 
+       /* Kick cpufreq (see the comment in linux/cpufreq.h). */
+       if (cpu_of(rq) == smp_processor_id())
+               cpufreq_trigger_update(rq_clock(rq));
+
        schedstat_set(curr->se.statistics.exec_max,
                      max(curr->se.statistics.exec_max, delta_exec));