sched: speed up and simplify vslice calculations
speed up and simplify vslice calculations.
[ From: Mike Galbraith <efault@gmx.de>: build fix ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ec0569e..ae2d4b0 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -46,7 +46,7 @@
* Minimal preemption granularity for CPU-bound tasks:
* (default: 2 msec, units: nanoseconds)
*/
-unsigned int sysctl_sched_min_granularity __read_mostly = 2000000ULL;
+const_debug unsigned int sysctl_sched_nr_latency = 20;
/*
* sys_sched_yield() compat mode
@@ -222,8 +222,7 @@
static u64 __sched_period(unsigned long nr_running)
{
u64 period = sysctl_sched_latency;
- unsigned long nr_latency =
- sysctl_sched_latency / sysctl_sched_min_granularity;
+ unsigned long nr_latency = sysctl_sched_nr_latency;
if (unlikely(nr_running > nr_latency)) {
period *= nr_running;
@@ -245,11 +244,15 @@
static u64 __sched_vslice(unsigned long nr_running)
{
- u64 period = __sched_period(nr_running);
+ unsigned long period = sysctl_sched_latency;
+ unsigned long nr_latency = sysctl_sched_nr_latency;
- do_div(period, nr_running);
+ if (unlikely(nr_running > nr_latency))
+ nr_running = nr_latency;
- return period;
+ period /= nr_running;
+
+ return (u64)period;
}
/*