Commit 9439aab8 authored by Suresh Siddha's avatar Suresh Siddha Committed by Ingo Molnar

[PATCH] sched: fix newly idle load balance in case of SMT

In the presence of SMT, newly idle balance was never happening for
multi-core and SMP domains (even when both the logical siblings are

If thread 0 is already idle and when thread 1 is about to go to idle,
newly idle load balance always think that one of the threads is not idle
and skips doing the newly idle load balance for multi-core and SMP

This is because of the idle_cpu() macro, which checks if the current
process on a cpu is an idle process. But this is not the case for the
thread doing the load_balance_newidle().

Fix this by using runqueue's nr_running field instead of idle_cpu(). And
also skip the logic of 'only one idle cpu in the group will be doing
load balancing' during newly idle case.
Signed-off-by: default avatarSuresh Siddha <>
Signed-off-by: default avatarIngo Molnar <>
parent c41917df
......@@ -2235,7 +2235,7 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
rq = cpu_rq(i);
if (*sd_idle && !idle_cpu(i))
if (*sd_idle && rq->nr_running)
*sd_idle = 0;
/* Bias balancing toward cpus of our domain */
......@@ -2257,9 +2257,11 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
* First idle cpu or the first cpu(busiest) in this sched group
* is eligible for doing load balancing at this and above
* domains.
* domains. In the newly idle case, we will allow all the cpu's
* to do the newly idle load balance.
if (local_group && balance_cpu != this_cpu && balance) {
if (idle != CPU_NEWLY_IDLE && local_group &&
balance_cpu != this_cpu && balance) {
*balance = 0;
goto ret;
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment