summaryrefslogtreecommitdiffstats
path: root/kernel/sched/sched.h
diff options
context:
space:
mode:
authorPeter Zijlstra2012-08-08 21:46:40 +0200
committerThomas Gleixner2012-08-13 18:41:54 +0200
commita35b6466aabb051568b844e8c63f87a356d3d129 (patch)
treea5d38cce8290a60f6729f97591cfa25d545c6474 /kernel/sched/sched.h
parentsched/cleanups: Add load balance cpumask pointer to 'struct lb_env' (diff)
downloadkernel-qcow2-linux-a35b6466aabb051568b844e8c63f87a356d3d129.tar.gz
kernel-qcow2-linux-a35b6466aabb051568b844e8c63f87a356d3d129.tar.xz
kernel-qcow2-linux-a35b6466aabb051568b844e8c63f87a356d3d129.zip
sched, cgroup: Reduce rq->lock hold times for large cgroup hierarchies
Peter Portante reported that for large cgroup hierarchies (and or on large CPU counts) we get immense lock contention on rq->lock and stuff stops working properly. His workload was a ton of processes, each in their own cgroup, everybody idling except for a sporadic wakeup once every so often. It was found that: schedule() idle_balance() load_balance() local_irq_save() double_rq_lock() update_h_load() walk_tg_tree(tg_load_down) tg_load_down() Results in an entire cgroup hierarchy walk under rq->lock for every new-idle balance and since new-idle balance isn't throttled this results in a lot of work while holding the rq->lock. This patch does two things, it removes the work from under rq->lock based on the good principle of race and pray which is widely employed in the load-balancer as a whole. And secondly it throttles the update_h_load() calculation to max once per jiffy. I considered excluding update_h_load() for new-idle balance all-together, but purely relying on regular balance passes to update this data might not work out under some rare circumstances where the new-idle busiest isn't the regular busiest for a while (unlikely, but a nightmare to debug if someone hits it and suffers). Cc: pjt@google.com Cc: Larry Woodman <lwoodman@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Reported-by: Peter Portante <pportant@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/n/tip-aaarrzfpnaam7pqrekofu8a6@git.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/sched/sched.h')
-rw-r--r--kernel/sched/sched.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c35a1a7dd4d6..531411b1044e 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -374,7 +374,11 @@ struct rq {
#ifdef CONFIG_FAIR_GROUP_SCHED
/* list of leaf cfs_rq on this cpu: */
struct list_head leaf_cfs_rq_list;
-#endif
+#ifdef CONFIG_SMP
+ unsigned long h_load_throttle;
+#endif /* CONFIG_SMP */
+#endif /* CONFIG_FAIR_GROUP_SCHED */
+
#ifdef CONFIG_RT_GROUP_SCHED
struct list_head leaf_rt_rq_list;
#endif