[PATCH 17/30] sched: persistent average load per task

Peter Zijlstra
2008-06-27T12:09:19Z

[-- Attachment #1: sched-avg_load_per_task.patch --]
[-- Type: text/plain, Size: 1815 bytes --]

Remove the fall-back to SCHED_LOAD_SCALE by remembering the previous value of
cpu_avg_load_per_task() - this is useful because of the hierarchical group
model in which task weight can be much smaller.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/sched.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -554,6 +554,8 @@ struct rq {
int cpu;
int online;

+ unsigned long avg_load_per_task;
+
struct task_struct *migration_thread;
struct list_head migration_queue;
#endif
@@ -1427,9 +1429,18 @@ static inline void dec_cpu_load(struct r
#ifdef CONFIG_SMP
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
-static unsigned long cpu_avg_load_per_task(int cpu);
static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);

+static unsigned long cpu_avg_load_per_task(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ if (rq->nr_running)
+ rq->avg_load_per_task = rq->load.weight / rq->nr_running;
+
+ return rq->avg_load_per_task;
+}
+
#ifdef CONFIG_FAIR_GROUP_SCHED

typedef void (*tg_visitor)(struct task_group *, int, struct sched_domain *);
@@ -2011,18 +2022,6 @@ static unsigned long target_load(int cpu
}

/*
- * Return the average load per task on the cpu's run queue
- */
-static unsigned long cpu_avg_load_per_task(int cpu)
-{
- struct rq *rq = cpu_rq(cpu);
- unsigned long total = weighted_cpuload(cpu);
- unsigned long n = rq->nr_running;
-
- return n ? total / n : SCHED_LOAD_SCALE;
-}
-
-/*
* find_idlest_group finds and returns the least busy CPU group within the
* domain.
*/

--