[PATCH RFC v7 06/12] blk-mq: Record active_queues_shared_sbitmap per tag_set for when using shared sbitmap

John Garry
2020-06-10T17:33:37Z

For when using a shared sbitmap, no longer should the number of active
request queues per hctx be relied on for when judging how to share the tag
bitmap.

Instead maintain the number of active request queues per tag_set, and make
the judgment based on that.

And since the blk_mq_tags.active_queues is no longer maintained, do not
show it in debugfs.

Originally-from: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: John Garry <john.garry@huawei.com>
---
block/blk-mq-debugfs.c | 25 ++++++++++++++++++++--
block/blk-mq-tag.c | 47 ++++++++++++++++++++++++++++++++----------
block/blk-mq.c | 2 ++
include/linux/blk-mq.h | 1 +
include/linux/blkdev.h | 1 +
5 files changed, 63 insertions(+), 13 deletions(-)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 0fa3af41ab65..05b4be0c03d9 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -458,17 +458,37 @@ static void blk_mq_debugfs_tags_show(struct seq_file *m,
}
}

+static void blk_mq_debugfs_tags_shared_sbitmap_show(struct seq_file *m,
+ struct blk_mq_tags *tags)
+{
+ seq_printf(m, "nr_tags=%u\n", tags->nr_tags);
+ seq_printf(m, "nr_reserved_tags=%u\n", tags->nr_reserved_tags);
+
+ seq_puts(m, "\nbitmap_tags:\n");
+ sbitmap_queue_show(tags->bitmap_tags, m);
+
+ if (tags->nr_reserved_tags) {
+ seq_puts(m, "\nbreserved_tags:\n");
+ sbitmap_queue_show(tags->breserved_tags, m);
+ }
+}
+
static int hctx_tags_show(void *data, struct seq_file *m)
{
struct blk_mq_hw_ctx *hctx = data;
struct request_queue *q = hctx->queue;
+ struct blk_mq_tag_set *set = q->tag_set;
int res;

res = mutex_lock_interruptible(&q->sysfs_lock);
if (res)
goto out;
- if (hctx->tags)
- blk_mq_debugfs_tags_show(m, hctx->tags);
+ if (hctx->tags) {
+ if (blk_mq_is_sbitmap_shared(set))
+ blk_mq_debugfs_tags_shared_sbitmap_show(m, hctx->tags);
+ else
+ blk_mq_debugfs_tags_show(m, hctx->tags);
+ }
mutex_unlock(&q->sysfs_lock);

out:
@@ -802,6 +822,7 @@ static const struct blk_mq_debugfs_attr blk_mq_debugfs_hctx_shared_sbitmap_attrs
{"dispatch", 0400, .seq_ops = &hctx_dispatch_seq_ops},
{"busy", 0400, hctx_busy_show},
{"ctx_map", 0400, hctx_ctx_map_show},
+ {"tags", 0400, hctx_tags_show},
{"sched_tags", 0400, hctx_sched_tags_show},
{"sched_tags_bitmap", 0400, hctx_sched_tags_bitmap_show},
{"io_poll", 0600, hctx_io_poll_show, hctx_io_poll_write},
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 7db16e49f6f6..6ca06b1c3a99 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -23,9 +23,19 @@
*/
bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
{
- if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
- !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
- atomic_inc(&hctx->tags->active_queues);
+ struct request_queue *q = hctx->queue;
+ struct blk_mq_tag_set *set = q->tag_set;
+
+ if (blk_mq_is_sbitmap_shared(set)){
+ if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) &&
+ !test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
+ atomic_inc(&set->active_queues_shared_sbitmap);
+
+ } else {
+ if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
+ !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
+ atomic_inc(&hctx->tags->active_queues);
+ }

return true;
}
@@ -47,11 +57,19 @@ void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
{
struct blk_mq_tags *tags = hctx->tags;
-
- if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
- return;
-
- atomic_dec(&tags->active_queues);
+ struct request_queue *q = hctx->queue;
+ struct blk_mq_tag_set *set = q->tag_set;
+
+ if (blk_mq_is_sbitmap_shared(q->tag_set)){
+ if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
+ &q->queue_flags))
+ return;
+ atomic_dec(&set->active_queues_shared_sbitmap);
+ } else {
+ if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
+ return;
+ atomic_dec(&tags->active_queues);
+ }

blk_mq_tag_wakeup_all(tags, false);
}
@@ -65,12 +83,11 @@ static inline bool hctx_may_queue(struct blk_mq_alloc_data *data,
{
struct blk_mq_hw_ctx *hctx = data->hctx;
struct request_queue *q = data->q;
+ struct blk_mq_tag_set *set = q->tag_set;
unsigned int depth, users;

if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED))
return true;
- if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
- return true;

/*
* Don't try dividing an ant
@@ -78,7 +95,15 @@ static inline bool hctx_may_queue(struct blk_mq_alloc_data *data,
if (bt->sb.depth == 1)
return true;

- users = atomic_read(&hctx->tags->active_queues);
+ if (blk_mq_is_sbitmap_shared(q->tag_set)) {
+ if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &q->queue_flags))
+ return true;
+ users = atomic_read(&set->active_queues_shared_sbitmap);
+ } else {
+ if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
+ return true;
+ users = atomic_read(&hctx->tags->active_queues);
+ }
if (!users)
return true;

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0f7e062a1665..f73a2f9c58bd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3350,6 +3350,8 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
goto out_free_mq_map;

if (blk_mq_is_sbitmap_shared(set)) {
+ atomic_set(&set->active_queues_shared_sbitmap, 0);
+
if (!blk_mq_init_shared_sbitmap(set)) {
ret = -ENOMEM;
goto out_free_mq_rq_maps;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 7b31cdb92a71..66711c7234db 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -252,6 +252,7 @@ struct blk_mq_tag_set {
unsigned int timeout;
unsigned int flags;
void *driver_data;
+ atomic_t active_queues_shared_sbitmap;

struct sbitmap_queue __bitmap_tags;
struct sbitmap_queue __breserved_tags;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c536278bec9e..1b0087e8d01a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -619,6 +619,7 @@ struct request_queue {
#define QUEUE_FLAG_PCI_P2PDMA 25 /* device supports PCI p2p requests */
#define QUEUE_FLAG_ZONE_RESETALL 26 /* supports Zone Reset All */
#define QUEUE_FLAG_RQ_ALLOC_TIME 27 /* record rq->alloc_time_ns */
+#define QUEUE_FLAG_HCTX_ACTIVE 28 /* at least one blk-mq hctx is active */

#define QUEUE_FLAG_MQ_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_SAME_COMP))
--
2.26.2