From: Siddha, Suresh B Date: Sat, 10 Sep 2005 07:26:21 +0000 (-0700) Subject: [PATCH] sched: don't kick ALB in the presence of pinned task X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=fa3b6ddc3f4a8eadba52234134cdb59c28b5332d;p=openwrt%2Fstaging%2Fblogic.git [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 Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/sched.c b/kernel/sched.c index 103f705b245c..1dc29dec38a9 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -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 @@ out_balanced: 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. */