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},
I had been pondering this, too, when creating v6. Problem is that it'll
show the tags per hctx, but as they are shared I guess the list looks
pretty identical per hctx.
Right, so my main concern in this series is debugfs, and how to present
the tag/hctx info. We can hide things under the hood mostly, but not so
much for debugfs.
So I guess we should filter the tags per hctx to have only those active
on that hctx displayed. But when doing so we can only print the
in-flight tags, the others are not assigned to a hctx and as such we
can't make a decision on which hctx they'll end up.
So we filter the tags in 7/12, and that should be ok.
But a concern is that we present identical hctx_tags_show() ->
blk_mq_debugfs_shared_sitmap_show() -> sbitmap_queue_show() per-hctx
info, which may be inappropriate/misleading/wrong. I need to audit that
more thoroughly.
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;
}
At one point someone would need to educate me what this double
'test_bit' and 'test_and_set_bit' is supposed to achieve.
Other than deliberately injecting a race condition ...
As I see, it's not a dangerous race, and meant as a performance
optimization.
test_bit() should be is quick compared to test_and_set_bit(), so nicer
to avoid always doing a test_and_set_bit().
So if we race with failed test_bit() calls and have multiple attempts
with the test_and_set_bit(), only 1 will succeed and do the increment.
@@ -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;
I'm not sure if we should present this in debugfs. It is not according
to this series.
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))
Other than that it looks fine.
Cheers
