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[PATCH] sched: don't kick ALB in the presence of pinned task 

Jack Steiner brought this issue at my OLS talk.

Take a scenario where two tasks are pinned to two HT threads in a physical
package.  Idle packages in the system will keep kicking migration_thread on
the busy package with out any success.

We will run into similar scenarios in the presence of CMP/NUMA.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Siddha, Suresh B 2005-09-10 00:26:21 -07:00 committed by Linus Torvalds
parent 5927ad78ec
commit fa3b6ddc3f
1 changed files with 14 additions and 1 deletions
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15
kernel/sched.c
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@ -2125,6 +2125,16 @@ static int load_balance(int this_cpu, runqueue_t *this_rq,
if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
spin_lock(&busiest->lock);
/* don't kick the migration_thread, if the curr
* task on busiest cpu can't be moved to this_cpu
*/
if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) {
spin_unlock(&busiest->lock);
all_pinned = 1;
goto out_one_pinned;
}
if (!busiest->active_balance) {
busiest->active_balance = 1;
busiest->push_cpu = this_cpu;
@ -2165,6 +2175,8 @@ static int load_balance(int this_cpu, runqueue_t *this_rq,
schedstat_inc(sd, lb_balanced[idle]);
sd->nr_balance_failed = 0;
out_one_pinned:
/* tune up the balancing interval */
if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
(sd->balance_interval < sd->max_interval))
@ -2357,7 +2369,8 @@ static void rebalance_tick(int this_cpu, runqueue_t *this_rq,
if (j - sd->last_balance >= interval) {
if (load_balance(this_cpu, this_rq, sd, idle)) {
/* We've pulled tasks over so either we're no
/*
* We've pulled tasks over so either we're no
* longer idle, or one of our SMT siblings is
* not idle.
*/