[tip:irq/core] genirq/affinity: Assign vectors to all present CPUs

[tip-bot for Christoph Hellwig]

Commit-ID:  9a0ef98e186d86fb3c1ff3ec267a76f067005f74
Gitweb:     http://git.kernel.org/tip/9a0ef98e186d86fb3c1ff3ec267a76f067005f74
Author:     Christoph Hellwig <hch@xxxxxx>
AuthorDate: Tue, 20 Jun 2017 01:37:55 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Thu, 22 Jun 2017 18:21:26 +0200

genirq/affinity: Assign vectors to all present CPUs

Currently the irq vector spread algorithm is restricted to online CPUs,
which ties the IRQ mapping to the currently online devices and doesn't deal
nicely with the fact that CPUs could come and go rapidly due to e.g. power
management.

Instead assign vectors to all present CPUs to avoid this churn.

Build a map of all possible CPUs for a given node, as the architectures
only provide a map of all onlines CPUs. Do this dynamically on each call
for the vector assingments, which is a bit suboptimal and could be
optimized in the future by provinding a mapping from the arch code.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: linux-block@xxxxxxxxxxxxxxx
Cc: Sagi Grimberg <sagi@xxxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: linux-nvme@xxxxxxxxxxxxxxxxxxx
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170603140403.27379-5-hch@xxxxxx

---
 kernel/irq/affinity.c | 76 ++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 63 insertions(+), 13 deletions(-)

diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index e2d356d..d2747f9 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -1,4 +1,7 @@
-
+/*
+ * Copyright (C) 2016 Thomas Gleixner.
+ * Copyright (C) 2016-2017 Christoph Hellwig.
+ */
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
@@ -35,13 +38,54 @@ static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
 	}
 }
 
-static int get_nodes_in_cpumask(const struct cpumask *mask, nodemask_t *nodemsk)
+static cpumask_var_t *alloc_node_to_present_cpumask(void)
+{
+	cpumask_var_t *masks;
+	int node;
+
+	masks = kcalloc(nr_node_ids, sizeof(cpumask_var_t), GFP_KERNEL);
+	if (!masks)
+		return NULL;
+
+	for (node = 0; node < nr_node_ids; node++) {
+		if (!zalloc_cpumask_var(&masks[node], GFP_KERNEL))
+			goto out_unwind;
+	}
+
+	return masks;
+
+out_unwind:
+	while (--node >= 0)
+		free_cpumask_var(masks[node]);
+	kfree(masks);
+	return NULL;
+}
+
+static void free_node_to_present_cpumask(cpumask_var_t *masks)
+{
+	int node;
+
+	for (node = 0; node < nr_node_ids; node++)
+		free_cpumask_var(masks[node]);
+	kfree(masks);
+}
+
+static void build_node_to_present_cpumask(cpumask_var_t *masks)
+{
+	int cpu;
+
+	for_each_present_cpu(cpu)
+		cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
+}
+
+static int get_nodes_in_cpumask(cpumask_var_t *node_to_present_cpumask,
+				const struct cpumask *mask, nodemask_t *nodemsk)
 {
 	int n, nodes = 0;
 
 	/* Calculate the number of nodes in the supplied affinity mask */
-	for_each_online_node(n) {
-		if (cpumask_intersects(mask, cpumask_of_node(n))) {
+	for_each_node(n) {
+		if (cpumask_intersects(mask, node_to_present_cpumask[n])) {
 			node_set(n, *nodemsk);
 			nodes++;
 		}
@@ -64,7 +108,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 	int last_affv = affv + affd->pre_vectors;
 	nodemask_t nodemsk = NODE_MASK_NONE;
 	struct cpumask *masks;
-	cpumask_var_t nmsk;
+	cpumask_var_t nmsk, *node_to_present_cpumask;
 
 	if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
 		return NULL;
@@ -73,13 +117,19 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 	if (!masks)
 		goto out;
 
+	node_to_present_cpumask = alloc_node_to_present_cpumask();
+	if (!node_to_present_cpumask)
+		goto out;
+
 	/* Fill out vectors at the beginning that don't need affinity */
 	for (curvec = 0; curvec < affd->pre_vectors; curvec++)
 		cpumask_copy(masks + curvec, irq_default_affinity);
 
 	/* Stabilize the cpumasks */
 	get_online_cpus();
-	nodes = get_nodes_in_cpumask(cpu_online_mask, &nodemsk);
+	build_node_to_present_cpumask(node_to_present_cpumask);
+	nodes = get_nodes_in_cpumask(node_to_present_cpumask, cpu_present_mask,
+				     &nodemsk);
 
 	/*
 	 * If the number of nodes in the mask is greater than or equal the
@@ -87,7 +137,8 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 	 */
 	if (affv <= nodes) {
 		for_each_node_mask(n, nodemsk) {
-			cpumask_copy(masks + curvec, cpumask_of_node(n));
+			cpumask_copy(masks + curvec,
+				     node_to_present_cpumask[n]);
 			if (++curvec == last_affv)
 				break;
 		}
@@ -101,7 +152,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 		vecs_per_node = (affv - (curvec - affd->pre_vectors)) / nodes;
 
 		/* Get the cpus on this node which are in the mask */
-		cpumask_and(nmsk, cpu_online_mask, cpumask_of_node(n));
+		cpumask_and(nmsk, cpu_present_mask, node_to_present_cpumask[n]);
 
 		/* Calculate the number of cpus per vector */
 		ncpus = cpumask_weight(nmsk);
@@ -133,6 +184,7 @@ done:
 	/* Fill out vectors at the end that don't need affinity */
 	for (; curvec < nvecs; curvec++)
 		cpumask_copy(masks + curvec, irq_default_affinity);
+	free_node_to_present_cpumask(node_to_present_cpumask);
 out:
 	free_cpumask_var(nmsk);
 	return masks;
@@ -147,12 +199,10 @@ int irq_calc_affinity_vectors(int maxvec, const struct irq_affinity *affd)
 {
 	int resv = affd->pre_vectors + affd->post_vectors;
 	int vecs = maxvec - resv;
-	int cpus;
+	int ret;
 
-	/* Stabilize the cpumasks */
 	get_online_cpus();
-	cpus = cpumask_weight(cpu_online_mask);
+	ret = min_t(int, cpumask_weight(cpu_present_mask), vecs) + resv;
 	put_online_cpus();
-
-	return min(cpus, vecs) + resv;
+	return ret;
 }