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authorSiddha, Suresh B <suresh.b.siddha@intel.com>2007-05-08 00:32:51 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-08 11:15:17 -0700
commit46cb4b7c88fa5517f64b5bee42939ea3614cddcb (patch)
tree429b8092394974ae787bf0cfaefe5c7b6a1da782 /kernel/time
parentbdecea3a9282d529b54954f3f1e59877629baba1 (diff)
sched: dynticks idle load balancing
Fix the process idle load balancing in the presence of dynticks. cpus for which ticks are stopped will sleep till the next event wakes it up. Potentially these sleeps can be for large durations and during which today, there is no periodic idle load balancing being done. This patch nominates an owner among the idle cpus, which does the idle load balancing on behalf of the other idle cpus. And once all the cpus are completely idle, then we can stop this idle load balancing too. Checks added in fast path are minimized. Whenever there are busy cpus in the system, there will be an owner(idle cpu) doing the system wide idle load balancing. Open items: 1. Intelligent owner selection (like an idle core in a busy package). 2. Merge with rcu's nohz_cpu_mask? Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/tick-sched.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f4fc867f467..3483e6cb954 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -217,6 +217,14 @@ void tick_nohz_stop_sched_tick(void)
* the scheduler tick in nohz_restart_sched_tick.
*/
if (!ts->tick_stopped) {
+ if (select_nohz_load_balancer(1)) {
+ /*
+ * sched tick not stopped!
+ */
+ cpu_clear(cpu, nohz_cpu_mask);
+ goto out;
+ }
+
ts->idle_tick = ts->sched_timer.expires;
ts->tick_stopped = 1;
ts->idle_jiffies = last_jiffies;
@@ -285,6 +293,7 @@ void tick_nohz_restart_sched_tick(void)
now = ktime_get();
local_irq_disable();
+ select_nohz_load_balancer(0);
tick_do_update_jiffies64(now);
cpu_clear(cpu, nohz_cpu_mask);