[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 idle). 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 domains. 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: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -2235,7 +2235,7 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
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rq = cpu_rq(i);
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if (*sd_idle && !idle_cpu(i))
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if (*sd_idle && rq->nr_running)
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*sd_idle = 0;
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/* Bias balancing toward cpus of our domain */
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@ -2257,9 +2257,11 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
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/*
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* First idle cpu or the first cpu(busiest) in this sched group
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* is eligible for doing load balancing at this and above
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* domains.
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* domains. In the newly idle case, we will allow all the cpu's
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* to do the newly idle load balance.
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*/
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if (local_group && balance_cpu != this_cpu && balance) {
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if (idle != CPU_NEWLY_IDLE && local_group &&
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balance_cpu != this_cpu && balance) {
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*balance = 0;
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goto ret;
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}
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