From 83d7f2424741c9dc76c21377c9d00d47abaf88df Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Mon, 4 Aug 2014 13:23:28 -0400 Subject: [PATCH] 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 Signed-off-by: Peter Zijlstra 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 Link: http://lkml.kernel.org/r/1407173008-9334-3-git-send-email-riel@redhat.com Signed-off-by: Ingo Molnar --- 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 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); }