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@lst.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-nvme@lists.infradead.org
Cc: Keith Busch <keith.busch@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170603140403.27379-5-hch@lst.de

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;
@@ -73,21 +117,28 @@ 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
 	 * number of vectors we just spread the vectors across the nodes.
 	 */
 	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 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 	/* 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;
 }