linux/kernel/irq/affinity.c
Christoph Hellwig 84676c1f21 genirq/affinity: assign vectors to all possible CPUs
Currently we assign managed interrupt vectors to all present CPUs.  This
works fine for systems were we only online/offline CPUs.  But in case of
systems that support physical CPU hotplug (or the virtualized version of
it) this means the additional CPUs covered for in the ACPI tables or on
the command line are not catered for.  To fix this we'd either need to
introduce new hotplug CPU states just for this case, or we can start
assining vectors to possible but not present CPUs.

Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Tested-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Fixes: 4b855ad371 ("blk-mq: Create hctx for each present CPU")
Cc: linux-kernel@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-01-12 11:01:38 -07:00

221 lines
5.4 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2016 Thomas Gleixner.
* Copyright (C) 2016-2017 Christoph Hellwig.
*/
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/cpu.h>
static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
int cpus_per_vec)
{
const struct cpumask *siblmsk;
int cpu, sibl;
for ( ; cpus_per_vec > 0; ) {
cpu = cpumask_first(nmsk);
/* Should not happen, but I'm too lazy to think about it */
if (cpu >= nr_cpu_ids)
return;
cpumask_clear_cpu(cpu, nmsk);
cpumask_set_cpu(cpu, irqmsk);
cpus_per_vec--;
/* If the cpu has siblings, use them first */
siblmsk = topology_sibling_cpumask(cpu);
for (sibl = -1; cpus_per_vec > 0; ) {
sibl = cpumask_next(sibl, siblmsk);
if (sibl >= nr_cpu_ids)
break;
if (!cpumask_test_and_clear_cpu(sibl, nmsk))
continue;
cpumask_set_cpu(sibl, irqmsk);
cpus_per_vec--;
}
}
}
static cpumask_var_t *alloc_node_to_possible_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_possible_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_possible_cpumask(cpumask_var_t *masks)
{
int cpu;
for_each_possible_cpu(cpu)
cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
}
static int get_nodes_in_cpumask(cpumask_var_t *node_to_possible_cpumask,
const struct cpumask *mask, nodemask_t *nodemsk)
{
int n, nodes = 0;
/* Calculate the number of nodes in the supplied affinity mask */
for_each_node(n) {
if (cpumask_intersects(mask, node_to_possible_cpumask[n])) {
node_set(n, *nodemsk);
nodes++;
}
}
return nodes;
}
/**
* irq_create_affinity_masks - Create affinity masks for multiqueue spreading
* @nvecs: The total number of vectors
* @affd: Description of the affinity requirements
*
* Returns the masks pointer or NULL if allocation failed.
*/
struct cpumask *
irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
{
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;
struct cpumask *masks;
cpumask_var_t nmsk, *node_to_possible_cpumask;
/*
* If there aren't any vectors left after applying the pre/post
* vectors don't bother with assigning affinity.
*/
if (!affv)
return NULL;
if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
return NULL;
masks = kcalloc(nvecs, sizeof(*masks), GFP_KERNEL);
if (!masks)
goto out;
node_to_possible_cpumask = alloc_node_to_possible_cpumask();
if (!node_to_possible_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();
build_node_to_possible_cpumask(node_to_possible_cpumask);
nodes = get_nodes_in_cpumask(node_to_possible_cpumask, cpu_possible_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,
node_to_possible_cpumask[n]);
if (++curvec == last_affv)
break;
}
goto done;
}
for_each_node_mask(n, nodemsk) {
int ncpus, v, vecs_to_assign, vecs_per_node;
/* Spread the vectors per node */
vecs_per_node = (affv - (curvec - affd->pre_vectors)) / nodes;
/* Get the cpus on this node which are in the mask */
cpumask_and(nmsk, cpu_possible_mask, node_to_possible_cpumask[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 * (ncpus / vecs_to_assign);
for (v = 0; curvec < last_affv && v < vecs_to_assign;
curvec++, v++) {
cpus_per_vec = ncpus / vecs_to_assign;
/* Account for extra vectors to compensate rounding errors */
if (extra_vecs) {
cpus_per_vec++;
--extra_vecs;
}
irq_spread_init_one(masks + curvec, nmsk, cpus_per_vec);
}
if (curvec >= last_affv)
break;
--nodes;
}
done:
put_online_cpus();
/* 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_possible_cpumask(node_to_possible_cpumask);
out:
free_cpumask_var(nmsk);
return masks;
}
/**
* irq_calc_affinity_vectors - Calculate the optimal number of vectors
* @minvec: The minimum number of vectors available
* @maxvec: The maximum number of vectors available
* @affd: Description of the affinity requirements
*/
int irq_calc_affinity_vectors(int minvec, int maxvec, const struct irq_affinity *affd)
{
int resv = affd->pre_vectors + affd->post_vectors;
int vecs = maxvec - resv;
int ret;
if (resv > minvec)
return 0;
get_online_cpus();
ret = min_t(int, cpumask_weight(cpu_possible_mask), vecs) + resv;
put_online_cpus();
return ret;
}