Commit-ID: e790fb0ba64bfec158e1219d899cb588275d12ab
Gitweb: http://git.kernel.org/tip/e790fb0ba64bfec158e1219d899cb588275d12ab
Author: Gautham R Shenoy <ego@xxxxxxxxxx>
AuthorDate: Tue, 14 Apr 2009 10:25:35 +0530
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Tue, 14 Apr 2009 11:49:19 +0200
sched: Nominate a power-efficient ilb in select_nohz_balancer()
The CPU that first goes idle becomes the idle-load-balancer and remains
that until either it picks up a task or till all the CPUs of the system
goes idle.
Optimize this further to allow it to relinquish it's post
once all it's siblings in the power-aware sched_domain go idle, thereby
allowing the whole package-core to go idle. While relinquising the post,
nominate another an idle-load balancer from a semi-idle core/package.
Signed-off-by: Gautham R Shenoy <ego@xxxxxxxxxx>
Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <20090414045535.7645.31641.stgit@xxxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/sched.c | 18 +++++++++++++++++-
1 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index b0fefa3..36d213b 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4414,8 +4414,24 @@ int select_nohz_load_balancer(int stop_tick)
/* make me the ilb owner */
if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1)
return 1;
- } else if (atomic_read(&nohz.load_balancer) == cpu)
+ } else if (atomic_read(&nohz.load_balancer) == cpu) {
+ int new_ilb;
+
+ if (!(sched_smt_power_savings ||
+ sched_mc_power_savings))
+ return 1;
+ /*
+ * Check to see if there is a more power-efficient
+ * ilb.
+ */
+ new_ilb = find_new_ilb(cpu);
+ if (new_ilb < nr_cpu_ids && new_ilb != cpu) {
+ atomic_set(&nohz.load_balancer, -1);
+ resched_cpu(new_ilb);
+ return 0;
+ }
return 1;
+ }
} else {
if (!cpumask_test_cpu(cpu, nohz.cpu_mask))
return 0;
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|