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sched/topology: Avoid pointless rebuild 

Fix partition_sched_domains() to try and preserve the existing machine
wide domain instead of unconditionally destroying it. We do this by
attempting to allocate the new single domain, only when that fails to
we reuse the fallback_doms.

When using fallback_doms we need to first destroy and then recreate
because both the old and new could be backed by it.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ofer Levi(SW) <oferle@mellanox.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineet.Gupta1@synopsys.com <Vineet.Gupta1@synopsys.com>
Cc: rusty@rustcorp.com.au <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-08-08 12:16:24 +02:00 committed by Ingo Molnar
parent 77d1dfda0e
commit 09e0dd8e0f
1 changed files with 12 additions and 3 deletions
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15
kernel/sched/topology.c
View File

@ -1851,7 +1851,17 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
/* Let the architecture update CPU core mappings: */
new_topology = arch_update_cpu_topology();
n = doms_new ? ndoms_new : 0;
if (!doms_new) {
WARN_ON_ONCE(dattr_new);
n = 0;
doms_new = alloc_sched_domains(1);
if (doms_new) {
n = 1;
cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
}
} else {
n = ndoms_new;
}
/* Destroy deleted domains: */
for (i = 0; i < ndoms_cur; i++) {
@ -1867,11 +1877,10 @@ match1:
}
n = ndoms_cur;
if (doms_new == NULL) {
if (!doms_new) {
n = 0;
doms_new = &fallback_doms;
cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
WARN_ON_ONCE(dattr_new);
}
/* Build new domains: */