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authorKeith Busch <keith.busch@intel.com>2017-04-03 15:25:53 -0400
committerThomas Gleixner <tglx@linutronix.de>2017-04-04 11:57:28 +0200
commit7bf8222b9bd0ba867e18b7f4537b61ef2e92eee8 (patch)
treed8c2d6c9eaf946a10b35ca415752b2d15ddaaad5 /kernel
parent08e4e0d0456d0ca8427b2d1ddffa30f1c3e774d7 (diff)
irq/affinity: Fix CPU spread for unbalanced nodes
The irq_create_affinity_masks routine is responsible for assigning a number of interrupt vectors to CPUs. The optimal assignemnet will spread requested vectors to all CPUs, with the fewest CPUs sharing a vector. The algorithm may fail to assign some vectors to any CPUs if a node's CPU count is lower than the average number of vectors per node. These vectors are unusable and create an un-optimal spread. Recalculate the number of vectors to assign at each node iteration by using the remaining number of vectors and nodes to be assigned, not exceeding the number of CPUs in that node. This will guarantee that every CPU is assigned at least one vector. Signed-off-by: Keith Busch <keith.busch@intel.com> Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: linux-nvme@lists.infradead.org Link: http://lkml.kernel.org/r/1491247553-7603-1-git-send-email-keith.busch@intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/irq/affinity.c20
1 files changed, 11 insertions, 9 deletions
diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index 4544b115f5eb..dc529116f7e6 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -59,7 +59,7 @@ static int get_nodes_in_cpumask(const struct cpumask *mask, nodemask_t *nodemsk)
struct cpumask *
irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
{
- int n, nodes, vecs_per_node, cpus_per_vec, extra_vecs, curvec;
+ int n, nodes, cpus_per_vec, extra_vecs, curvec;
int affv = nvecs - affd->pre_vectors - affd->post_vectors;
int last_affv = affv + affd->pre_vectors;
nodemask_t nodemsk = NODE_MASK_NONE;
@@ -94,19 +94,21 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
goto done;
}
- /* Spread the vectors per node */
- vecs_per_node = affv / nodes;
- /* Account for rounding errors */
- extra_vecs = affv - (nodes * vecs_per_node);
-
for_each_node_mask(n, nodemsk) {
- int ncpus, v, vecs_to_assign = vecs_per_node;
+ int ncpus, v, vecs_to_assign, vecs_per_node;
+
+ /* Spread the vectors per node */
+ vecs_per_node = (affv - curvec) / nodes;
/* Get the cpus on this node which are in the mask */
cpumask_and(nmsk, cpu_online_mask, cpumask_of_node(n));
/* Calculate the number of cpus per vector */
ncpus = cpumask_weight(nmsk);
+ vecs_to_assign = min(vecs_per_node, ncpus);
+
+ /* Account for rounding errors */
+ extra_vecs = ncpus - vecs_to_assign;
for (v = 0; curvec < last_affv && v < vecs_to_assign;
curvec++, v++) {
@@ -115,14 +117,14 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
/* Account for extra vectors to compensate rounding errors */
if (extra_vecs) {
cpus_per_vec++;
- if (!--extra_vecs)
- vecs_per_node++;
+ --extra_vecs;
}
irq_spread_init_one(masks + curvec, nmsk, cpus_per_vec);
}
if (curvec >= last_affv)
break;
+ --nodes;
}
done: