sched/numa: Fix numa capacity computation (83d7f242) · Commits · 戴 / test

Commit 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>

kernel/sched/fair.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -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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