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sched: Fix SD_OVERLAP

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SD_OVERLAP exists to allow overlapping groups, overlapping groups
appear in NUMA topologies that aren't fully connected.

The typical result of not fully connected NUMA is that each cpu (or
rather node) will have different spans for a particular distance.
However due to how sched domains are traversed -- only the first cpu
in the mask goes one level up -- the next level only cares about the
spans of the cpus that went up.

Due to this two things were observed to be broken:

 - build_overlap_sched_groups() -- since its possible the cpu we're
   building the groups for exists in multiple (or all) groups, the
   selection criteria of the first group didn't ensure there was a cpu
   for which is was true that cpumask_first(span) == cpu. Thus load-
   balancing would terminate.

 - update_group_power() -- assumed that the cpu span of the first
   group of the domain was covered by all groups of the child domain.
   The above explains why this isn't true, so deal with it.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: David Rientjes <rientjes@google.com>
Link: http://lkml.kernel.org/r/1337788843.9783.14.camel@laptop
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2012-05-23 18:00:43 +02:00 committed by Ingo Molnar
parent 2ea45800d8
commit 74a5ce20e6
2 changed files with 25 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
kernel/sched/core.c
View File

@ -6030,11 +6030,14 @@ build_overlap_sched_groups(struct sched_domain *sd, int cpu)
cpumask_or(covered, covered, sg_span);
sg->sgp = *per_cpu_ptr(sdd->sgp, cpumask_first(sg_span));
sg->sgp = *per_cpu_ptr(sdd->sgp, i);
atomic_inc(&sg->sgp->ref);
if (cpumask_test_cpu(cpu, sg_span))
if ((!groups && cpumask_test_cpu(cpu, sg_span)) ||
cpumask_first(sg_span) == cpu) {
WARN_ON_ONCE(!cpumask_test_cpu(cpu, sg_span));
groups = sg;
}
if (!first)
first = sg;

25
kernel/sched/fair.c
View File

@ -3574,11 +3574,26 @@ void update_group_power(struct sched_domain *sd, int cpu)
power = 0;
group = child->groups;
do {
power += group->sgp->power;
group = group->next;
} while (group != child->groups);
if (child->flags & SD_OVERLAP) {
/*
* SD_OVERLAP domains cannot assume that child groups
* span the current group.
*/
for_each_cpu(cpu, sched_group_cpus(sdg))
power += power_of(cpu);
} else {
/*
* !SD_OVERLAP domains can assume that child groups
* span the current group.
*/
group = child->groups;
do {
power += group->sgp->power;
group = group->next;
} while (group != child->groups);
}
sdg->sgp->power = power;
}