sched: Pre-compute cpumask_weight(sched_domain_span(sd))

Dave reported that his large SPARC machines spend lots of time in
hweight64(), try and optimize some of those needless cpumask_weight()
invocations (esp. with the large offstack cpumasks these are very
expensive indeed).

Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e3e900f318d7..dfea40574b2a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -960,6 +960,7 @@ struct sched_domain {
         char *name;
 #endif
 
+        unsigned int span_weight;
         /*
          * Span of all CPUs in this domain.
          *