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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>
This commit is contained in:
Rik van Riel 2014-08-04 13:23:28 -04:00 committed by Ingo Molnar
parent b932c03c34
commit 83d7f24247
1 changed files with 8 additions and 3 deletions
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11
kernel/sched/fair.c
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@ -1038,7 +1038,8 @@ struct numa_stats {
*/ */
static void update_numa_stats(struct numa_stats *ns, int nid) 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)); memset(ns, 0, sizeof(*ns));
for_each_cpu(cpu, cpumask_of_node(nid)) { 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) if (!cpus)
return; return;
ns->task_capacity = /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE); 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); ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
} }