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authorRik van Riel <riel@redhat.com>2014-08-04 13:23:28 -0400
committerIngo Molnar <mingo@kernel.org>2014-08-12 12:48:23 +0200
commit83d7f2424741c9dc76c21377c9d00d47abaf88df (patch)
treeeddb9a5732788c00247c3bb430b14bea4bc6c953 /kernel/sched/fair.c
parentb932c03c34f3b03c7364c06aa8cae5b74609fc41 (diff)
sched/numa: Fix numa capacity computation
Commit c61037e9 fixes the phenomenon of 'fantom' cores due to N*frac(smt_power) >= 1 by limiting the capacity to the actual number of cores in the load balancing code. This patch applies the same correction to the NUMA balancing code. Signed-off-by: Rik van Riel <riel@redhat.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: mgorman@suse.de Cc: vincent.guittot@linaro.org Cc: Morten.Rasmussen@arm.com Cc: nicolas.pitre@linaro.org Cc: efault@gmx.de Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1407173008-9334-3-git-send-email-riel@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/fair.c')
-rw-r--r--kernel/sched/fair.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e1cf419c3c7f..1413c44ce8a1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1038,7 +1038,8 @@ struct numa_stats {
*/
static void update_numa_stats(struct numa_stats *ns, int nid)
{
- int cpu, cpus = 0;
+ int smt, cpu, cpus = 0;
+ unsigned long capacity;
memset(ns, 0, sizeof(*ns));
for_each_cpu(cpu, cpumask_of_node(nid)) {
@@ -1062,8 +1063,12 @@ static void update_numa_stats(struct numa_stats *ns, int nid)
if (!cpus)
return;
- ns->task_capacity =
- DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE);
+ /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
+ smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
+ capacity = cpus / smt; /* cores */
+
+ ns->task_capacity = min_t(unsigned, capacity,
+ DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
}