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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2007-08-25 18:41:53 +0200
committerIngo Molnar <mingo@elte.hu>2007-08-25 18:41:53 +0200
commit218050855ece4e923106ab614ac65afa0f618df3 (patch)
treef7b1234ce9e8ad0bc5d5af949949251240ec6a2c /kernel/sched.c
parent1fc84aaae3bae9646dd4c7798b8c0ff934338909 (diff)
sched: adaptive scheduler granularity
Instead of specifying the preemption granularity, specify the wanted latency. By fixing the granlarity to a constany the wakeup latency it a function of the number of running tasks on the rq. Invert this relation. sysctl_sched_granularity becomes a minimum for the dynamic granularity computed from the new sysctl_sched_latency. Then use this latency to do more intelligent granularity decisions: if there are fewer tasks running then we can schedule coarser. This helps performance while still always keeping the latency target. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 6798328a2e0..da26f46d50d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4911,14 +4911,18 @@ cpumask_t nohz_cpu_mask = CPU_MASK_NONE;
static inline void sched_init_granularity(void)
{
unsigned int factor = 1 + ilog2(num_online_cpus());
- const unsigned long gran_limit = 100000000;
+ const unsigned long limit = 100000000;
sysctl_sched_granularity *= factor;
- if (sysctl_sched_granularity > gran_limit)
- sysctl_sched_granularity = gran_limit;
+ if (sysctl_sched_granularity > limit)
+ sysctl_sched_granularity = limit;
- sysctl_sched_runtime_limit = sysctl_sched_granularity * 5;
- sysctl_sched_wakeup_granularity = sysctl_sched_granularity / 2;
+ sysctl_sched_latency *= factor;
+ if (sysctl_sched_latency > limit)
+ sysctl_sched_latency = limit;
+
+ sysctl_sched_runtime_limit = sysctl_sched_latency * 5;
+ sysctl_sched_wakeup_granularity = sysctl_sched_latency / 2;
}
#ifdef CONFIG_SMP