> > if (!is_cpu_exclusive(cur)) {
> > - cpus_or(pspan, pspan, cur->cpus_allowed);
> > if (cpus_equal(pspan, cur->cpus_allowed))
> > return;
> > cspan = CPU_MASK_NONE;
>
>
> I dont think this is a valid optimization. What we are checking here
> is if a previously exclusive cpuset has been changed to a non-exclusive one
> (echo 0 > cpu_exclusive), we then OR all the cpus in the current cpuset
> to the parent cpuset. We then rebuild a sched domain to include all of the cpus
> in the current cpuset and those in the parent not part of exclusive children
Not that it matters, but I don't think you need to OR in the current cpuset
cpus to the parents cpus (pspan) here, because they are already in pspan.
Look at the surrounding code:
pspan = par->cpus_allowed;
list_for_each_entry(c, &par->children, sibling) {
if (is_cpu_exclusive(c))
cpus_andnot(pspan, pspan, c->cpus_allowed);
}
if (!is_cpu_exclusive(cur)) {
cpus_or(pspan, pspan, cur->cpus_allowed);
if (cpus_equal(pspan, cur->cpus_allowed))
return;
cspan = CPU_MASK_NONE;
'pspan' starts out with all the parents cpus, which must be a superset
of currents cpus (cur->cpus_allowed.)
Then we subtract (cpus_andnot) from pspan the cpus in the cpu_exclusive
siblings of current. Since current is not cpu_exclusive, and since the
cpus of its cpu_exclusive sibling cpusets cannot overlap with currents
cpus, we could not have subtracted any current cpu from pspan.
So pspan is still a superset of currents cpus.
So OR'ing in currents cpus to pspan is a no-op.
--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <[email protected]> 1.925.600.0401
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