sched/{core,fair}: trigger OPP change request on fork()

Patch "sched/fair: add triggers for OPP change requests" introduced OPP
change triggers for enqueue_task_fair(), but the trigger was operating only
for wakeups. Fact is that it makes sense to consider wakeup_new also (i.e.,
fork()), as we don't know anything about a newly created task and thus we
most certainly want to jump to max OPP to not harm performance too much.

However, it is not currently possible (or at least it wasn't evident to me
how to do so :/) to tell new wakeups from other (non wakeup) operations.

This patch introduces an additional flag in sched.h that is only set at
fork() time and it is then consumed in enqueue_task_fair() for our purpose.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Steve Muckle <smuckle@linaro.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 23e82805ec470d7bad4465780d6b55218c065094..5c8d0dbaae5db694e54e195f755e741759ddcd1a 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2387,7 +2387,7 @@ void wake_up_new_task(struct task_struct *p)
 #endif
 
        rq = __task_rq_lock(p);
-       activate_task(rq, p, 0);
+       activate_task(rq, p, ENQUEUE_WAKEUP_NEW);
        p->on_rq = TASK_ON_RQ_QUEUED;
        trace_sched_wakeup_new(p);
        check_preempt_curr(rq, p, WF_FORK);

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 844788da00bea14eff07192c5fb462bf5242d46c..3937f79240df1b9006b99b3a8f1216e69980b052 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4171,7 +4171,8 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 {
        struct cfs_rq *cfs_rq;
        struct sched_entity *se = &p->se;
-       int task_new = !(flags & ENQUEUE_WAKEUP);
+       int task_new = flags & ENQUEUE_WAKEUP_NEW;
+       int task_wakeup = flags & ENQUEUE_WAKEUP;
 
        for_each_sched_entity(se) {
                if (se->on_rq)
@@ -4215,12 +4216,8 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
                 * because we get here also during load balancing, but
                 * in these cases it seems wise to trigger as single
                 * request after load balancing is done.
-                *
-                * XXX: how about fork()? Do we need a special
-                *      flag/something to tell if we are here after a
-                *      fork() (wakeup_task_new)?
                 */
-               if (!task_new)
+               if (task_new || task_wakeup)
                        update_capacity_of(cpu_of(rq));
        }
        hrtick_update(rq);

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ac28024b2d7a4129bef689880994e793ce2070a9..0052ada93ae8fc1099ba6dee7f804b990fa37828 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1181,6 +1181,7 @@ static const u32 prio_to_wmult[40] = {
 #endif
 #define ENQUEUE_REPLENISH      0x08
 #define ENQUEUE_RESTORE        0x10
+#define ENQUEUE_WAKEUP_NEW     0x20
 
 #define DEQUEUE_SLEEP          0x01
 #define DEQUEUE_SAVE           0x02