sched: avoid large irq-latencies in smp-balancing

SMP balancing is done with IRQs disabled and can iterate the full rq.
When rqs are large this can cause large irq-latencies. Limit the nr of
iterations on each run.

This fixes a scheduling latency regression reported by the -rt folks.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Tested-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 0 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index adddf682d4cb..3a1744fed2b6 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -301,6 +301,14 @@ static struct ctl_table kern_table[] = {
                 .mode           = 0644,
                 .proc_handler   = &proc_dointvec,
         },
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "sched_nr_migrate",
+                .data           = &sysctl_sched_nr_migrate,
+                .maxlen         = sizeof(unsigned int),
+                .mode           = 644,
+                .proc_handler   = &proc_dointvec,
+        },
 #endif
         {
                 .ctl_name       = CTL_UNNUMBERED,