[RFC tg_shares_up improvements - v1 09/12] sched: demand based update_cfs_load()

[pjt]

When the system is busy dilation of rq->next_balance makes lb->update_shares()
insufficiently frequent for threads which don't sleep (no dequeue/enqueue
updates).  Adjust for this by making demand based updates based on the
accumulation of execution time sufficient to wrap our averaging window.

Signed-off-by: Paul Turner <pjt@xxxxxxxxxx>

---
 kernel/sched.c      |    9 ++++++++-
 kernel/sched_fair.c |   10 ++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

Index: kernel/sched.c
===================================================================
--- kernel/sched.c.orig
+++ kernel/sched.c
@@ -355,9 +355,16 @@ struct cfs_rq {
 	 */
 	unsigned long h_load;
 
+	/*
+	 * Maintaining per-cpu shares distribution for group scheduling
+	 *
+	 * load_stamp is the last time we updated the load average
+	 * load_last is the last time we updated the load average and saw load
+	 * load_unacc_exec_time is currently unaccounted execution time
+	 */
 	u64 load_avg;
 	u64 load_period;
-	u64 load_stamp, load_last;
+	u64 load_stamp, load_last, load_unacc_exec_time;
 
 	unsigned long load_contribution;
 #endif
Index: kernel/sched_fair.c
===================================================================
--- kernel/sched_fair.c.orig
+++ kernel/sched_fair.c
@@ -538,6 +538,9 @@ static u64 sched_vslice(struct cfs_rq *c
 	return calc_delta_fair(sched_slice(cfs_rq, se), se);
 }
 
+static void update_cfs_load(struct cfs_rq *cfs_rq);
+static void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta);
+
 /*
  * Update the current task's runtime statistics. Skip current tasks that
  * are not in our scheduling class.
@@ -557,6 +560,12 @@ __update_curr(struct cfs_rq *cfs_rq, str
 
 	curr->vruntime += delta_exec_weighted;
 	update_min_vruntime(cfs_rq);
+
+	cfs_rq->load_unacc_exec_time += delta_exec;
+	if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
+		update_cfs_load(cfs_rq);
+		update_cfs_shares(cfs_rq, 0);
+	}
 }
 
 static void update_curr(struct cfs_rq *cfs_rq)
@@ -712,6 +721,7 @@ static void update_cfs_load(struct cfs_r
 	}
 
 	cfs_rq->load_stamp = now;
+	cfs_rq->load_unacc_exec_time = 0;
 	cfs_rq->load_period += delta;
 	if (load) {
 		cfs_rq->load_last = now;

-- 

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