sched: Add sysctl_sched_shares_window

Introduce a new sysctl for the shares window and disambiguate it from
sched_time_avg.

A 10ms window appears to be a good compromise between accuracy and performance.

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101115234938.112173964@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 15 insertions, 1 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index b320753aa6c9..6c84439ce987 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -89,6 +89,13 @@ unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
 
 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
 
+/*
+ * The exponential sliding  window over which load is averaged for shares
+ * distribution.
+ * (default: 10msec)
+ */
+unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
+
 static const struct sched_class fair_sched_class;
 
 /**************************************************************
@@ -688,7 +695,7 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
 #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
 static void update_cfs_load(struct cfs_rq *cfs_rq)
 {
-        u64 period = sched_avg_period();
+        u64 period = sysctl_sched_shares_window;
         u64 now, delta;
         unsigned long load = cfs_rq->load.weight;
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 3132b25193db..9b520d74f052 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -333,6 +333,13 @@ static struct ctl_table kern_table[] = {
                 .proc_handler   = proc_dointvec,
         },
         {
+                .procname       = "sched_shares_window",
+                .data           = &sysctl_sched_shares_window,
+                .maxlen         = sizeof(unsigned int),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec,
+        },
+        {
                 .procname       = "timer_migration",
                 .data           = &sysctl_timer_migration,
                 .maxlen         = sizeof(unsigned int),