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Subject[PATCH 2/8] Remove staggering of load balancing
Remove load staggering.

Timer interrupts already are staggered. We do not need an additional
layer of time staggering for short load balancing actions that take a
reasonably small portion of the time slice.

For load balancing on large sched_domains we will add a serialization
later that avoids concurrent load balance operations and thus has
the same effect as load staggering.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.19-rc5-mm1/kernel/sched.c
===================================================================
--- linux-2.6.19-rc5-mm1.orig/kernel/sched.c 2006-11-10 22:47:56.305271903 -0600
+++ linux-2.6.19-rc5-mm1/kernel/sched.c 2006-11-10 22:48:09.002647332 -0600
@@ -2844,16 +2844,10 @@ static void active_load_balance(struct r
* Balancing parameters are set up in arch_init_sched_domains.
*/

-/* Don't have all balancing operations going off at once: */
-static inline unsigned long cpu_offset(int cpu)
-{
- return jiffies + cpu * HZ / NR_CPUS;
-}
-
static void
rebalance_tick(int this_cpu, struct rq *this_rq, enum idle_type idle)
{
- unsigned long this_load, interval, j = cpu_offset(this_cpu);
+ unsigned long this_load, interval;
struct sched_domain *sd;
int i, scale;

@@ -2888,7 +2882,7 @@ rebalance_tick(int this_cpu, struct rq *
if (unlikely(!interval))
interval = 1;

- if (j - sd->last_balance >= interval) {
+ if (jiffies - sd->last_balance >= interval) {
if (load_balance(this_cpu, this_rq, sd, idle)) {
/*
* We've pulled tasks over so either we're no
-
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