[PATCH 5/8] blk-mq: allow the driver to pass in an affinity mask

Christoph Hellwig
2016-04-16T01:36:06Z

Allow drivers to pass in the affinity mask from the generic interrupt
layer, and spread queues based on that. If the driver doesn't pass in
a mask we will create it using the genirq helper. As this helper was
modelled after the blk-mq algorithm there should be no change in behavior.

XXX: Just as with the core IRQ spreading code this doesn't handle CPU
hotplug yet.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/Makefile | 2 +-
block/blk-mq-cpumap.c | 120 -------------------------------------------------
block/blk-mq.c | 60 ++++++++++++++++++++++++-
block/blk-mq.h | 8 ----
include/linux/blk-mq.h | 1 +
5 files changed, 60 insertions(+), 131 deletions(-)
delete mode 100644 block/blk-mq-cpumap.c

diff --git a/block/Makefile b/block/Makefile
index 9eda232..aeb318d 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -6,7 +6,7 @@ obj-$(CONFIG_BLOCK) := bio.o elevator.o blk-core.o blk-tag.o blk-sysfs.o \
blk-flush.o blk-settings.o blk-ioc.o blk-map.o \
blk-exec.o blk-merge.o blk-softirq.o blk-timeout.o \
blk-lib.o blk-mq.o blk-mq-tag.o \
- blk-mq-sysfs.o blk-mq-cpu.o blk-mq-cpumap.o ioctl.o \
+ blk-mq-sysfs.o blk-mq-cpu.o ioctl.o \
genhd.o scsi_ioctl.o partition-generic.o ioprio.o \
badblocks.o partitions/

diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
deleted file mode 100644
index d0634bc..0000000
--- a/block/blk-mq-cpumap.c
+++ /dev/null
@@ -1,120 +0,0 @@
-/*
- * CPU <-> hardware queue mapping helpers
- *
- * Copyright (C) 2013-2014 Jens Axboe
- */
-#include <linux/kernel.h>
-#include <linux/threads.h>
-#include <linux/module.h>
-#include <linux/mm.h>
-#include <linux/smp.h>
-#include <linux/cpu.h>
-
-#include <linux/blk-mq.h>
-#include "blk.h"
-#include "blk-mq.h"
-
-static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
- const int cpu)
-{
- return cpu * nr_queues / nr_cpus;
-}
-
-static int get_first_sibling(unsigned int cpu)
-{
- unsigned int ret;
-
- ret = cpumask_first(topology_sibling_cpumask(cpu));
- if (ret < nr_cpu_ids)
- return ret;
-
- return cpu;
-}
-
-int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
- const struct cpumask *online_mask)
-{
- unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
- cpumask_var_t cpus;
-
- if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
- return 1;
-
- cpumask_clear(cpus);
- nr_cpus = nr_uniq_cpus = 0;
- for_each_cpu(i, online_mask) {
- nr_cpus++;
- first_sibling = get_first_sibling(i);
- if (!cpumask_test_cpu(first_sibling, cpus))
- nr_uniq_cpus++;
- cpumask_set_cpu(i, cpus);
- }
-
- queue = 0;
- for_each_possible_cpu(i) {
- if (!cpumask_test_cpu(i, online_mask)) {
- map[i] = 0;
- continue;
- }
-
- /*
- * Easy case - we have equal or more hardware queues. Or
- * there are no thread siblings to take into account. Do
- * 1:1 if enough, or sequential mapping if less.
- */
- if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
- map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
- queue++;
- continue;
- }
-
- /*
- * Less then nr_cpus queues, and we have some number of
- * threads per cores. Map sibling threads to the same
- * queue.
- */
- first_sibling = get_first_sibling(i);
- if (first_sibling == i) {
- map[i] = cpu_to_queue_index(nr_uniq_cpus, nr_queues,
- queue);
- queue++;
- } else
- map[i] = map[first_sibling];
- }
-
- free_cpumask_var(cpus);
- return 0;
-}
-
-unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set)
-{
- unsigned int *map;
-
- /* If cpus are offline, map them to first hctx */
- map = kzalloc_node(sizeof(*map) * nr_cpu_ids, GFP_KERNEL,
- set->numa_node);
- if (!map)
- return NULL;
-
- if (!blk_mq_update_queue_map(map, set->nr_hw_queues, cpu_online_mask))
- return map;
-
- kfree(map);
- return NULL;
-}
-
-/*
- * We have no quick way of doing reverse lookups. This is only used at
- * queue init time, so runtime isn't important.
- */
-int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
-{
- int i;
-
- for_each_possible_cpu(i) {
- if (index == mq_map[i])
- return local_memory_node(cpu_to_node(i));
- }
-
- return NUMA_NO_NODE;
-}
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1699baf..ab156bb 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -22,6 +22,7 @@
#include <linux/sched/sysctl.h>
#include <linux/delay.h>
#include <linux/crash_dump.h>
+#include <linux/interrupt.h>

#include <trace/events/block.h>

@@ -1954,6 +1955,22 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
}
EXPORT_SYMBOL(blk_mq_init_queue);

+/*
+ * We have no quick way of doing reverse lookups. This is only used at
+ * queue init time, so runtime isn't important.
+ */
+static int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
+{
+ int i;
+
+ for_each_possible_cpu(i) {
+ if (index == mq_map[i])
+ return local_memory_node(cpu_to_node(i));
+ }
+
+ return NUMA_NO_NODE;
+}
+
static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
struct request_queue *q)
{
@@ -2013,6 +2030,30 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
blk_mq_sysfs_register(q);
}

+static unsigned int *
+affinity_mask_to_queue_map(const struct cpumask *affinity_mask, int node)
+{
+ unsigned int *map;
+ int queue = -1, cpu = 0;
+
+ map = kzalloc_node(sizeof(*map) * nr_cpu_ids, GFP_KERNEL, node);
+ if (!map)
+ return NULL;
+
+ if (!affinity_mask)
+ return map; /* map all cpus to queue 0 */
+
+ /* If cpus are offline, map them to first hctx */
+ for_each_online_cpu(cpu) {
+ if (cpumask_test_cpu(cpu, affinity_mask))
+ queue++;
+ if (queue > 0)
+ map[cpu] = queue;
+ }
+
+ return map;
+}
+
struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
struct request_queue *q)
{
@@ -2028,7 +2069,21 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
if (!q->queue_hw_ctx)
goto err_percpu;

- q->mq_map = blk_mq_make_queue_map(set);
+ if (set->affinity_mask) {
+ q->mq_map = affinity_mask_to_queue_map(set->affinity_mask,
+ set->numa_node);
+ } else {
+ struct cpumask *affinity_mask;
+ int ret;
+
+ ret = irq_create_affinity_mask(&affinity_mask, set->nr_hw_queues);
+ if (ret)
+ goto err_map;
+
+ q->mq_map = affinity_mask_to_queue_map(affinity_mask, set->numa_node);
+ kfree(affinity_mask);
+ }
+
if (!q->mq_map)
goto err_map;

@@ -2111,7 +2166,8 @@ static void blk_mq_queue_reinit(struct request_queue *q,

blk_mq_sysfs_unregister(q);

- blk_mq_update_queue_map(q->mq_map, q->nr_hw_queues, online_mask);
+// XXX: figure out what to do about cpu hotplug in the new world order
+// blk_mq_update_queue_map(q->mq_map, q->nr_hw_queues, online_mask);

/*
* redo blk_mq_init_cpu_queues and blk_mq_init_hw_queues. FIXME: maybe
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 9087b11..fe7e21f 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -45,14 +45,6 @@ void blk_mq_enable_hotplug(void);
void blk_mq_disable_hotplug(void);

/*
- * CPU -> queue mappings
- */
-extern unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set);
-extern int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
- const struct cpumask *online_mask);
-extern int blk_mq_hw_queue_to_node(unsigned int *map, unsigned int);
-
-/*
* sysfs helpers
*/
extern int blk_mq_sysfs_register(struct request_queue *q);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 2498fdf..21ffe10 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -74,6 +74,7 @@ struct blk_mq_tag_set {
unsigned int timeout;
unsigned int flags; /* BLK_MQ_F_* */
void *driver_data;
+ struct cpumask *affinity_mask;

struct blk_mq_tags **tags;

--
2.1.4