sched/core: Optimize pick_next_task() for idle_sched_class
authorPeter Zijlstra <peterz@infradead.org>
Thu, 19 Jan 2017 17:44:08 +0000 (18:44 +0100)
committerIngo Molnar <mingo@kernel.org>
Mon, 30 Jan 2017 10:46:34 +0000 (11:46 +0100)
commit49ee576809d837442624ac18804b07943267cd57
treed30473970c09cd2d7b9c3dc3c368de0a7cd066ab
parent3a09b8d45b3c05d49e581831de626927c37599f8
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