Messages in this thread Patch in this message | | | Date | Mon, 30 Jan 2017 03:54:24 -0800 | From | tip-bot for Peter Zijlstra <> | Subject | [tip:sched/core] sched/core: Optimize pick_next_task() for idle_sched_class |
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Commit-ID: 49ee576809d837442624ac18804b07943267cd57 Gitweb: http://git.kernel.org/tip/49ee576809d837442624ac18804b07943267cd57 Author: Peter Zijlstra <peterz@infradead.org> AuthorDate: Thu, 19 Jan 2017 18:44:08 +0100 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Mon, 30 Jan 2017 11:46:34 +0100
sched/core: Optimize pick_next_task() for idle_sched_class
Steve noticed that when we switch from IDLE to SCHED_OTHER we fail to take the shortcut, even though all runnable tasks are of the fair class, because prev->sched_class != &fair_sched_class.
Since I reworked the put_prev_task() stuff, we don't really care about prev->class here, so removing that condition will allow this case.
This increases the likely case from 78% to 98% correct for Steve's workload.
Reported-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20170119174408.GN6485@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org> --- kernel/sched/core.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 49ce1cb..51ca21e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3321,15 +3321,14 @@ static inline void schedule_debug(struct task_struct *prev) static inline struct task_struct * pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { - const struct sched_class *class = &fair_sched_class; + const struct sched_class *class; struct task_struct *p; /* * Optimization: we know that if all tasks are in * the fair class we can call that function directly: */ - if (likely(prev->sched_class == class && - rq->nr_running == rq->cfs.h_nr_running)) { + if (likely(rq->nr_running == rq->cfs.h_nr_running)) { p = fair_sched_class.pick_next_task(rq, prev, rf); if (unlikely(p == RETRY_TASK)) goto again;
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