Commit-ID: df1c99d416500da8d26a4d78777467c53ee7689e
Gitweb: http://git.kernel.org/tip/df1c99d416500da8d26a4d78777467c53ee7689e
Author: "Mike Galbraith" <efault@xxxxxx>
AuthorDate: Tue, 10 Mar 2009 19:08:11 +0100
Commit: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 11 Mar 2009 11:31:50 +0100
sched: add avg_overlap decay
Impact: more precise avg_overlap metric - better load-balancing
avg_overlap is used to measure the runtime overlap of the waker and
wakee.
However, when a process changes behaviour, eg a pipe becomes
un-congested and we don't need to go to sleep after a wakeup
for a while, the avg_overlap value grows stale.
When running we use the avg runtime between preemption as a
measure for avg_overlap since the amount of runtime can be
correlated to cache footprint.
The longer we run, the less likely we'll be wanting to be
migrated to another CPU.
Signed-off-by: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <1236709131.25234.576.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/sched.c | 24 +++++++++++++++++++++++-
1 files changed, 23 insertions(+), 1 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index af5cd1b..2f28351 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4620,6 +4620,28 @@ static inline void schedule_debug(struct task_struct *prev)
#endif
}
+static void put_prev_task(struct rq *rq, struct task_struct *prev)
+{
+ if (prev->state == TASK_RUNNING) {
+ u64 runtime = prev->se.sum_exec_runtime;
+
+ runtime -= prev->se.prev_sum_exec_runtime;
+ runtime = min_t(u64, runtime, 2*sysctl_sched_migration_cost);
+
+ /*
+ * In order to avoid avg_overlap growing stale when we are
+ * indeed overlapping and hence not getting put to sleep, grow
+ * the avg_overlap on preemption.
+ *
+ * We use the average preemption runtime because that
+ * correlates to the amount of cache footprint a task can
+ * build up.
+ */
+ update_avg(&prev->se.avg_overlap, runtime);
+ }
+ prev->sched_class->put_prev_task(rq, prev);
+}
+
/*
* Pick up the highest-prio task:
*/
@@ -4698,7 +4720,7 @@ need_resched_nonpreemptible:
if (unlikely(!rq->nr_running))
idle_balance(cpu, rq);
- prev->sched_class->put_prev_task(rq, prev);
+ put_prev_task(rq, prev);
next = pick_next_task(rq);
if (likely(prev != next)) {
--
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