Commit-ID: 83d7f2424741c9dc76c21377c9d00d47abaf88df
Gitweb: http://git.kernel.org/tip/83d7f2424741c9dc76c21377c9d00d47abaf88df
Author: Rik van Riel <riel@xxxxxxxxxx>
AuthorDate: Mon, 4 Aug 2014 13:23:28 -0400
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 12 Aug 2014 12:48:23 +0200
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@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: mgorman@xxxxxxx
Cc: vincent.guittot@xxxxxxxxxx
Cc: Morten.Rasmussen@xxxxxxx
Cc: nicolas.pitre@xxxxxxxxxx
Cc: efault@xxxxxx
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1407173008-9334-3-git-send-email-riel@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e1cf419..1413c44 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);
}
--
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