From: Suresh Siddha Date: Thu, 19 Jul 2007 19:28:35 +0000 (+0200) Subject: [PATCH] sched: fix newly idle load balance in case of SMT X-Git-Tag: v2.6.23-rc1~261^2~2 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9439aab8dbc33c2c03c3a19dba267360383ba38c;p=linux-2.6 [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 Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched.c b/kernel/sched.c index 645256b228..e36d99d1dd 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -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; }