From: Nick Piggin <piggin@cyberone.com.au>

I think this might be causing problems.  Maybe its there for a reason, but
if so then I think some more work needs to be done.

An idle CPU will be unable to pull tasks from a runqueue if they have all
been run very recently.  This patch changes that.  Maybe it overbalances on
other loads.  It would be good to try those benchmarks on it...



 kernel/sched.c |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)

diff -puN kernel/sched.c~sched-cpu-migration-fix kernel/sched.c
--- 25/kernel/sched.c~sched-cpu-migration-fix	2003-08-26 01:42:36.000000000 -0700
+++ 25-akpm/kernel/sched.c	2003-08-26 01:42:36.000000000 -0700
@@ -1125,7 +1125,7 @@ can_migrate_task(task_t *tsk, runqueue_t
 {
 	unsigned long delta = sched_clock() - tsk->timestamp;
 
-	if (idle && (delta <= JIFFIES_TO_NS(cache_decay_ticks)))
+	if (!idle && (delta <= JIFFIES_TO_NS(cache_decay_ticks)))
 		return 0;
 	if (task_running(rq, tsk))
 		return 0;
@@ -1276,15 +1276,17 @@ static void rebalance_tick(runqueue_t *t
 			load_balance(this_rq, idle, cpu_to_node_mask(this_cpu));
 			spin_unlock(&this_rq->lock);
 		}
-	}
+
+	} else {
 #ifdef CONFIG_NUMA
-	if (!(j % BUSY_NODE_REBALANCE_TICK))
-		balance_node(this_rq, idle, this_cpu);
+		if (!(j % BUSY_NODE_REBALANCE_TICK))
+			balance_node(this_rq, idle, this_cpu);
 #endif
-	if (!(j % BUSY_REBALANCE_TICK)) {
-		spin_lock(&this_rq->lock);
-		load_balance(this_rq, 0, cpu_to_node_mask(this_cpu));
-		spin_unlock(&this_rq->lock);
+		if (!(j % BUSY_REBALANCE_TICK)) {
+			spin_lock(&this_rq->lock);
+			load_balance(this_rq, idle, cpu_to_node_mask(this_cpu));
+			spin_unlock(&this_rq->lock);
+		}
 	}
 }
 #else

_