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

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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>
This commit is contained in:
Peter Zijlstra
2010-04-16 14:59:29 +02:00
committed by Ingo Molnar
parent 74f5187ac8
commit 669c55e9f9
3 changed files with 9 additions and 7 deletions
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3
kernel/sched.c
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@@ -6271,6 +6271,9 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
struct rq *rq = cpu_rq(cpu);
struct sched_domain *tmp;
for (tmp = sd; tmp; tmp = tmp->parent)
tmp->span_weight = cpumask_weight(sched_domain_span(tmp));
/* Remove the sched domains which do not contribute to scheduling. */
for (tmp = sd; tmp; ) {
struct sched_domain *parent = tmp->parent;