Commit-ID: 09e0dd8e0f2e197690d34fed8cb4737114d3dd5f
Gitweb: http://git.kernel.org/tip/09e0dd8e0f2e197690d34fed8cb4737114d3dd5f
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 8 Aug 2017 12:16:24 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 25 Aug 2017 11:12:20 +0200
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@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Ofer Levi(SW) <oferle@xxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vineet.Gupta1@xxxxxxxxxxxx <Vineet.Gupta1@xxxxxxxxxxxx>
Cc: rusty@xxxxxxxxxxxxxxx <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/topology.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 179b90b..727daa2 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -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: */
--
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