xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

sched: Rework pick_next_task() slow-path

Browse Source 
Avoid the RETRY_TASK case in the pick_next_task() slow path.

By doing the put_prev_task() early, we get the rt/deadline pull done,
and by testing rq->nr_running we know if we need newidle_balance().

This then gives a stable state to pick a task from.

Since the fast-path is fair only; it means the other classes will
always have pick_next_task(.prev=NULL, .rf=NULL) and we can simplify.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Aaron Lu <aaron.lwe@gmail.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: mingo@kernel.org
Cc: Phil Auld <pauld@redhat.com>
Cc: Julien Desfossez <jdesfossez@digitalocean.com>
Cc: Nishanth Aravamudan <naravamudan@digitalocean.com>
Link: https://lkml.kernel.org/r/aa34d24b36547139248f32a30138791ac6c02bd6.1559129225.git.vpillai@digitalocean.com
This commit is contained in:
Peter Zijlstra
2019-05-29 20:36:44 +00:00
parent 5f2a45fc9e
commit 67692435c4
7 changed files with 34 additions and 73 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
kernel/sched/rt.c
View File

@@ -1553,38 +1553,11 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
struct task_struct *p;
struct rt_rq *rt_rq = &rq->rt;
if (need_pull_rt_task(rq, prev)) {
/*
* This is OK, because current is on_cpu, which avoids it being
* picked for load-balance and preemption/IRQs are still
* disabled avoiding further scheduler activity on it and we're
* being very careful to re-start the picking loop.
*/
rq_unpin_lock(rq, rf);
pull_rt_task(rq);
rq_repin_lock(rq, rf);
/*
* pull_rt_task() can drop (and re-acquire) rq->lock; this
* means a dl or stop task can slip in, in which case we need
* to re-start task selection.
*/
if (unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
rq->dl.dl_nr_running))
return RETRY_TASK;
}
/*
* We may dequeue prev's rt_rq in put_prev_task().
* So, we update time before rt_queued check.
*/
if (prev->sched_class == &rt_sched_class)
update_curr_rt(rq);
WARN_ON_ONCE(prev || rf);
if (!rt_rq->rt_queued)
return NULL;
put_prev_task(rq, prev);
p = _pick_next_task_rt(rq);
set_next_task_rt(rq, p);