sched: Introduce primitives to account for CFS bandwidth tracking

In this patch we introduce the notion of CFS bandwidth, partitioned into
globally unassigned bandwidth, and locally claimed bandwidth.

 - The global bandwidth is per task_group, it represents a pool of unclaimed
   bandwidth that cfs_rqs can allocate from.
 - The local bandwidth is tracked per-cfs_rq, this represents allotments from
   the global pool bandwidth assigned to a specific cpu.

Bandwidth is managed via cgroupfs, adding two new interfaces to the cpu subsystem:
 - cpu.cfs_period_us : the bandwidth period in usecs
 - cpu.cfs_quota_us : the cpu bandwidth (in usecs) that this tg will be allowed
   to consume over period above.

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Nikhil Rao <ncrao@google.com>
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184756.972636699@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 16 insertions, 0 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index f86b0cb5eb29..f24f4171019d 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1234,6 +1234,22 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
                 check_preempt_tick(cfs_rq, curr);
 }
 
+
+/**************************************************
+ * CFS bandwidth control machinery
+ */
+
+#ifdef CONFIG_CFS_BANDWIDTH
+/*
+ * default period for cfs group bandwidth.
+ * default: 0.1s, units: nanoseconds
+ */
+static inline u64 default_cfs_period(void)
+{
+        return 100000000ULL;
+}
+#endif
+
 /**************************************************
  * CFS operations on tasks:
  */