[PATCH 20/30] sched: fix load scaling in group balancing

Peter Zijlstra
2008-06-27T12:08:35Z

[-- Attachment #1: sched-fix-load_balance-h_load.patch --]
[-- Type: text/plain, Size: 1673 bytes --]

doing the load balance will change cfs_rq->load.weight (that's the whole point)
but since that's part of the scale factor, we'll scale back with a different
amount.

Weight getting smaller would result in an inflated moved_load which causes
it to stop balancing too soon.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
kernel/sched_fair.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -1449,6 +1449,8 @@ load_balance_fair(struct rq *this_rq, in

list_for_each_entry(tg, &task_groups, list) {
struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu];
+ unsigned long busiest_h_load = busiest_cfs_rq->h_load;
+ unsigned long busiest_weight = busiest_cfs_rq->load.weight;
long rem_load, moved_load;

/*
@@ -1457,8 +1459,8 @@ load_balance_fair(struct rq *this_rq, in
if (!busiest_cfs_rq->task_weight)
continue;

- rem_load = rem_load_move * busiest_cfs_rq->load.weight;
- rem_load /= busiest_cfs_rq->h_load + 1;
+ rem_load = rem_load_move * busiest_weight;
+ rem_load /= busiest_h_load + 1;

moved_load = __load_balance_fair(this_rq, this_cpu, busiest,
rem_load, sd, idle, all_pinned, this_best_prio,
@@ -1467,8 +1469,8 @@ load_balance_fair(struct rq *this_rq, in
if (!moved_load)
continue;

- moved_load *= busiest_cfs_rq->h_load;
- moved_load /= busiest_cfs_rq->load.weight + 1;
+ moved_load *= busiest_h_load;
+ moved_load /= busiest_weight + 1;

rem_load_move -= moved_load;
if (rem_load_move < 0)

--