[PATCH V3 for 5.11 00/12] blk-mq/scsi: tracking device queue depth via sbitmap

[PATCH V3 for 5.11 00/12] blk-mq/scsi: tracking device queue depth via sbitmap

[Ming Lei]

Hi,

scsi uses one global atomic variable to track queue depth for each
LUN/request queue. This way can't scale well when there is lots of CPU
cores and the disk is very fast. Broadcom guys has complained that their
high end HBA can't reach top performance because .device_busy is
operated in IO path.

Replace the atomic variable sdev->device_busy with sbitmap for
tracking scsi device queue depth.

Test on scsi_debug shows this way improve IOPS > 20%. Meantime
the IOPS difference is just ~1% compared with bypassing .device_busy
on scsi_debug via patches[1]

The 1st 6 patches moves percpu allocation hint into sbitmap, since
the improvement by doing percpu allocation hint on sbitmap is observable.
Meantime export helpers for SCSI.

Patch 7 and 8 prepares for the conversion by returning budget token
from .get_budget callback, meantime passes the budget token to driver
via 'struct blk_mq_queue_data' in .queue_rq().

The last four patches changes SCSI for switching to track device queue
depth via sbitmap.

The patchset have been tested by Broadcom, and obvious performance boost
can be observed.

Given it is based on both for-5.10/block and 5.10/scsi-queue, the target
is for v5.11. And it is posted out just for getting full/enough review.

Please comment and review!

V3:
	- rebase on both for-5.10/block and 5.10/scsi-queue.

V2:
	- fix one build failure


Ming Lei (12):
  sbitmap: remove sbitmap_clear_bit_unlock
  sbitmap: maintain allocation round_robin in sbitmap
  sbitmap: add helpers for updating allocation hint
  sbitmap: move allocation hint into sbitmap
  sbitmap: export sbitmap_weight
  sbitmap: add helper of sbitmap_calculate_shift
  blk-mq: add callbacks for storing & retrieving budget token
  blk-mq: return budget token from .get_budget callback
  scsi: put hot fields of scsi_host_template into one cacheline
  scsi: add scsi_device_busy() to read sdev->device_busy
  scsi: make sure sdev->queue_depth is <= shost->can_queue
  scsi: replace sdev->device_busy with sbitmap

 block/blk-mq-sched.c                 |  17 ++-
 block/blk-mq.c                       |  38 +++--
 block/blk-mq.h                       |  25 +++-
 block/kyber-iosched.c                |   3 +-
 drivers/message/fusion/mptsas.c      |   2 +-
 drivers/scsi/mpt3sas/mpt3sas_scsih.c |   2 +-
 drivers/scsi/scsi.c                  |   4 +
 drivers/scsi/scsi_lib.c              |  69 ++++++---
 drivers/scsi/scsi_priv.h             |   1 +
 drivers/scsi/scsi_scan.c             |  22 ++-
 drivers/scsi/scsi_sysfs.c            |   4 +-
 drivers/scsi/sg.c                    |   2 +-
 include/linux/blk-mq.h               |  13 +-
 include/linux/sbitmap.h              |  84 +++++++----
 include/scsi/scsi_cmnd.h             |   2 +
 include/scsi/scsi_device.h           |   8 +-
 include/scsi/scsi_host.h             |  72 ++++-----
 lib/sbitmap.c                        | 213 +++++++++++++++------------
 18 files changed, 376 insertions(+), 205 deletions(-)

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>

-- 
2.25.2

[PATCH V3 for 5.11 01/12] sbitmap: remove sbitmap_clear_bit_unlock

[Ming Lei]

No one uses this helper any more, so kill it.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/sbitmap.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index e40d019c3d9d..51edc05489cb 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -320,12 +320,6 @@ static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int b
 	set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
 }
 
-static inline void sbitmap_clear_bit_unlock(struct sbitmap *sb,
-					    unsigned int bitnr)
-{
-	clear_bit_unlock(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
-}
-
 static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
 {
 	return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
-- 
2.25.2

[PATCH V3 for 5.11 02/12] sbitmap: maintain allocation round_robin in sbitmap

[Ming Lei]

Now allocation round_robin info is maintained by sbitmap_queue.

Actually, bit allocation belongs to sbitmap. Also the following
patch will move alloc_hint to sbitmap for users with high depth.

So move round_robin to sbitmap.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq.c          |  2 +-
 block/kyber-iosched.c   |  3 ++-
 include/linux/sbitmap.h | 20 ++++++++++----------
 lib/sbitmap.c           | 28 ++++++++++++++--------------
 4 files changed, 27 insertions(+), 26 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index e04b759add75..45149970b891 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2684,7 +2684,7 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
 		goto free_cpumask;
 
 	if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
-				gfp, node))
+				gfp, node, false))
 		goto free_ctxs;
 	hctx->nr_ctx = 0;
 
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index dc89199bc8c6..cc8bcfe1d587 100644
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -479,7 +479,8 @@ static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
 
 	for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
 		if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
-				      ilog2(8), GFP_KERNEL, hctx->numa_node)) {
+				      ilog2(8), GFP_KERNEL, hctx->numa_node,
+				      false)) {
 			while (--i >= 0)
 				sbitmap_free(&khd->kcq_map[i]);
 			goto err_kcqs;
diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index 51edc05489cb..68097b052ec3 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -61,6 +61,11 @@ struct sbitmap {
 	 */
 	unsigned int map_nr;
 
+	/**
+	 * @round_robin: Allocate bits in strict round-robin order.
+	 */
+	bool round_robin;
+
 	/**
 	 * @map: Allocated bitmap.
 	 */
@@ -129,11 +134,6 @@ struct sbitmap_queue {
 	 */
 	atomic_t ws_active;
 
-	/**
-	 * @round_robin: Allocate bits in strict round-robin order.
-	 */
-	bool round_robin;
-
 	/**
 	 * @min_shallow_depth: The minimum shallow depth which may be passed to
 	 * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
@@ -149,11 +149,14 @@ struct sbitmap_queue {
  *         given, a good default is chosen.
  * @flags: Allocation flags.
  * @node: Memory node to allocate on.
+ * @round_robin: If true, be stricter about allocation order; always allocate
+ *               starting from the last allocated bit. This is less efficient
+ *               than the default behavior (false).
  *
  * Return: Zero on success or negative errno on failure.
  */
 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
-		      gfp_t flags, int node);
+		      gfp_t flags, int node, bool round_robin);
 
 /**
  * sbitmap_free() - Free memory used by a &struct sbitmap.
@@ -179,15 +182,12 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth);
  * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
  * @sb: Bitmap to allocate from.
  * @alloc_hint: Hint for where to start searching for a free bit.
- * @round_robin: If true, be stricter about allocation order; always allocate
- *               starting from the last allocated bit. This is less efficient
- *               than the default behavior (false).
  *
  * This operation provides acquire barrier semantics if it succeeds.
  *
  * Return: Non-negative allocated bit number if successful, -1 otherwise.
  */
-int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin);
+int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint);
 
 /**
  * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 267aa7709416..8d920d66d42a 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -42,7 +42,7 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
 }
 
 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
-		      gfp_t flags, int node)
+		      gfp_t flags, int node, bool round_robin)
 {
 	unsigned int bits_per_word;
 	unsigned int i;
@@ -67,6 +67,7 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
 	sb->shift = shift;
 	sb->depth = depth;
 	sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
+	sb->round_robin = round_robin;
 
 	if (depth == 0) {
 		sb->map = NULL;
@@ -137,14 +138,14 @@ static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
 }
 
 static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
-				     unsigned int alloc_hint, bool round_robin)
+				     unsigned int alloc_hint)
 {
 	int nr;
 
 	do {
 		nr = __sbitmap_get_word(&sb->map[index].word,
 					sb->map[index].depth, alloc_hint,
-					!round_robin);
+					!sb->round_robin);
 		if (nr != -1)
 			break;
 		if (!sbitmap_deferred_clear(sb, index))
@@ -154,7 +155,7 @@ static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
 	return nr;
 }
 
-int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin)
+int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
 {
 	unsigned int i, index;
 	int nr = -1;
@@ -166,14 +167,13 @@ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin)
 	 * alloc_hint to find the right word index. No point in looping
 	 * twice in find_next_zero_bit() for that case.
 	 */
-	if (round_robin)
+	if (sb->round_robin)
 		alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
 	else
 		alloc_hint = 0;
 
 	for (i = 0; i < sb->map_nr; i++) {
-		nr = sbitmap_find_bit_in_index(sb, index, alloc_hint,
-						round_robin);
+		nr = sbitmap_find_bit_in_index(sb, index, alloc_hint);
 		if (nr != -1) {
 			nr += index << sb->shift;
 			break;
@@ -358,7 +358,8 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 	int ret;
 	int i;
 
-	ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node);
+	ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node,
+				round_robin);
 	if (ret)
 		return ret;
 
@@ -390,7 +391,6 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 		atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
 	}
 
-	sbq->round_robin = round_robin;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
@@ -432,12 +432,12 @@ int __sbitmap_queue_get(struct sbitmap_queue *sbq)
 		hint = depth ? prandom_u32() % depth : 0;
 		this_cpu_write(*sbq->alloc_hint, hint);
 	}
-	nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin);
+	nr = sbitmap_get(&sbq->sb, hint);
 
 	if (nr == -1) {
 		/* If the map is full, a hint won't do us much good. */
 		this_cpu_write(*sbq->alloc_hint, 0);
-	} else if (nr == hint || unlikely(sbq->round_robin)) {
+	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
 		/* Only update the hint if we used it. */
 		hint = nr + 1;
 		if (hint >= depth - 1)
@@ -468,7 +468,7 @@ int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 	if (nr == -1) {
 		/* If the map is full, a hint won't do us much good. */
 		this_cpu_write(*sbq->alloc_hint, 0);
-	} else if (nr == hint || unlikely(sbq->round_robin)) {
+	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
 		/* Only update the hint if we used it. */
 		hint = nr + 1;
 		if (hint >= depth - 1)
@@ -584,7 +584,7 @@ void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 	smp_mb__after_atomic();
 	sbitmap_queue_wake_up(sbq);
 
-	if (likely(!sbq->round_robin && nr < sbq->sb.depth))
+	if (likely(!sbq->sb.round_robin && nr < sbq->sb.depth))
 		*per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
@@ -641,7 +641,7 @@ void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
 	}
 	seq_puts(m, "}\n");
 
-	seq_printf(m, "round_robin=%d\n", sbq->round_robin);
+	seq_printf(m, "round_robin=%d\n", sbq->sb.round_robin);
 	seq_printf(m, "min_shallow_depth=%u\n", sbq->min_shallow_depth);
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_show);
-- 
2.25.2

[PATCH V3 for 5.11 03/12] sbitmap: add helpers for updating allocation hint

[Ming Lei]

Add helpers for updating allocation hint, so that we can
avoid to duplicate code.

Prepare for moving allocation hint into sbitmap.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 lib/sbitmap.c | 93 ++++++++++++++++++++++++++++++---------------------
 1 file changed, 54 insertions(+), 39 deletions(-)

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 8d920d66d42a..4e4423414f4d 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -9,6 +9,55 @@
 #include <linux/sbitmap.h>
 #include <linux/seq_file.h>
 
+static int init_alloc_hint(struct sbitmap_queue *sbq, gfp_t flags)
+{
+	unsigned depth = sbq->sb.depth;
+
+	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
+	if (!sbq->alloc_hint)
+		return -ENOMEM;
+
+	if (depth && !sbq->sb.round_robin) {
+		int i;
+
+		for_each_possible_cpu(i)
+			*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
+	}
+
+	return 0;
+}
+
+static inline unsigned update_alloc_hint_before_get(struct sbitmap_queue *sbq,
+						    unsigned int depth)
+{
+	unsigned hint;
+
+	hint = this_cpu_read(*sbq->alloc_hint);
+	if (unlikely(hint >= depth)) {
+		hint = depth ? prandom_u32() % depth : 0;
+		this_cpu_write(*sbq->alloc_hint, hint);
+	}
+
+	return hint;
+}
+
+static inline void update_alloc_hint_after_get(struct sbitmap_queue *sbq,
+					       unsigned int depth,
+					       unsigned int hint,
+					       unsigned int nr)
+{
+	if (nr == -1) {
+		/* If the map is full, a hint won't do us much good. */
+		this_cpu_write(*sbq->alloc_hint, 0);
+	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
+		/* Only update the hint if we used it. */
+		hint = nr + 1;
+		if (hint >= depth - 1)
+			hint = 0;
+		this_cpu_write(*sbq->alloc_hint, hint);
+	}
+}
+
 /*
  * See if we have deferred clears that we can batch move
  */
@@ -363,17 +412,11 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 	if (ret)
 		return ret;
 
-	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
-	if (!sbq->alloc_hint) {
+	if (init_alloc_hint(sbq, flags) != 0) {
 		sbitmap_free(&sbq->sb);
 		return -ENOMEM;
 	}
 
-	if (depth && !round_robin) {
-		for_each_possible_cpu(i)
-			*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
-	}
-
 	sbq->min_shallow_depth = UINT_MAX;
 	sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
 	atomic_set(&sbq->wake_index, 0);
@@ -426,24 +469,10 @@ int __sbitmap_queue_get(struct sbitmap_queue *sbq)
 	unsigned int hint, depth;
 	int nr;
 
-	hint = this_cpu_read(*sbq->alloc_hint);
 	depth = READ_ONCE(sbq->sb.depth);
-	if (unlikely(hint >= depth)) {
-		hint = depth ? prandom_u32() % depth : 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
-	}
+	hint = update_alloc_hint_before_get(sbq, depth);
 	nr = sbitmap_get(&sbq->sb, hint);
-
-	if (nr == -1) {
-		/* If the map is full, a hint won't do us much good. */
-		this_cpu_write(*sbq->alloc_hint, 0);
-	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
-		/* Only update the hint if we used it. */
-		hint = nr + 1;
-		if (hint >= depth - 1)
-			hint = 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
-	}
+	update_alloc_hint_after_get(sbq, depth, hint, nr);
 
 	return nr;
 }
@@ -457,24 +486,10 @@ int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 
 	WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);
 
-	hint = this_cpu_read(*sbq->alloc_hint);
 	depth = READ_ONCE(sbq->sb.depth);
-	if (unlikely(hint >= depth)) {
-		hint = depth ? prandom_u32() % depth : 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
-	}
+	hint = update_alloc_hint_before_get(sbq, depth);
 	nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);
-
-	if (nr == -1) {
-		/* If the map is full, a hint won't do us much good. */
-		this_cpu_write(*sbq->alloc_hint, 0);
-	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
-		/* Only update the hint if we used it. */
-		hint = nr + 1;
-		if (hint >= depth - 1)
-			hint = 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
-	}
+	update_alloc_hint_after_get(sbq, depth, hint, nr);
 
 	return nr;
 }
-- 
2.25.2

[PATCH V3 for 5.11 04/12] sbitmap: move allocation hint into sbitmap

[Ming Lei]

Allocation hint should have belonged to sbitmap, also when sbitmap's
depth is high and no need to use mulitple wakeup queues, user can
benefit from percpu allocation hint too.

So move allocation hint into sbitmap.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq.c          |   2 +-
 block/kyber-iosched.c   |   2 +-
 include/linux/sbitmap.h |  41 ++++++++------
 lib/sbitmap.c           | 115 ++++++++++++++++++++++++----------------
 4 files changed, 97 insertions(+), 63 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 45149970b891..88154cea83d8 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2684,7 +2684,7 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
 		goto free_cpumask;
 
 	if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
-				gfp, node, false))
+				gfp, node, false, false))
 		goto free_ctxs;
 	hctx->nr_ctx = 0;
 
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index cc8bcfe1d587..3949d68ac4c1 100644
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -480,7 +480,7 @@ static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
 	for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
 		if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
 				      ilog2(8), GFP_KERNEL, hctx->numa_node,
-				      false)) {
+				      false, false)) {
 			while (--i >= 0)
 				sbitmap_free(&khd->kcq_map[i]);
 			goto err_kcqs;
diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index 68097b052ec3..103b41c03311 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -70,6 +70,14 @@ struct sbitmap {
 	 * @map: Allocated bitmap.
 	 */
 	struct sbitmap_word *map;
+
+	/*
+	 * @alloc_hint: Cache of last successfully allocated or freed bit.
+	 *
+	 * This is per-cpu, which allows multiple users to stick to different
+	 * cachelines until the map is exhausted.
+	 */
+	unsigned int __percpu *alloc_hint;
 };
 
 #define SBQ_WAIT_QUEUES 8
@@ -105,14 +113,6 @@ struct sbitmap_queue {
 	 */
 	struct sbitmap sb;
 
-	/*
-	 * @alloc_hint: Cache of last successfully allocated or freed bit.
-	 *
-	 * This is per-cpu, which allows multiple users to stick to different
-	 * cachelines until the map is exhausted.
-	 */
-	unsigned int __percpu *alloc_hint;
-
 	/**
 	 * @wake_batch: Number of bits which must be freed before we wake up any
 	 * waiters.
@@ -152,11 +152,13 @@ struct sbitmap_queue {
  * @round_robin: If true, be stricter about allocation order; always allocate
  *               starting from the last allocated bit. This is less efficient
  *               than the default behavior (false).
+ * @alloc_hint: If true, apply percpu hint for where to start searching for
+ * 		a free bit.
  *
  * Return: Zero on success or negative errno on failure.
  */
 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
-		      gfp_t flags, int node, bool round_robin);
+		      gfp_t flags, int node, bool round_robin, bool alloc_hint);
 
 /**
  * sbitmap_free() - Free memory used by a &struct sbitmap.
@@ -164,6 +166,7 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
  */
 static inline void sbitmap_free(struct sbitmap *sb)
 {
+	free_percpu(sb->alloc_hint);
 	kfree(sb->map);
 	sb->map = NULL;
 }
@@ -181,19 +184,17 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth);
 /**
  * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
  * @sb: Bitmap to allocate from.
- * @alloc_hint: Hint for where to start searching for a free bit.
  *
  * This operation provides acquire barrier semantics if it succeeds.
  *
  * Return: Non-negative allocated bit number if successful, -1 otherwise.
  */
-int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint);
+int sbitmap_get(struct sbitmap *sb);
 
 /**
  * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
  * limiting the depth used from each word.
  * @sb: Bitmap to allocate from.
- * @alloc_hint: Hint for where to start searching for a free bit.
  * @shallow_depth: The maximum number of bits to allocate from a single word.
  *
  * This rather specific operation allows for having multiple users with
@@ -205,8 +206,7 @@ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint);
  *
  * Return: Non-negative allocated bit number if successful, -1 otherwise.
  */
-int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
-			unsigned long shallow_depth);
+int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth);
 
 /**
  * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
@@ -320,6 +320,18 @@ static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int b
 	set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
 }
 
+/*
+ * Pair of sbitmap_get, and this one applies both cleared bit and
+ * allocation hint.
+ */
+static inline void sbitmap_put(struct sbitmap *sb, unsigned int bitnr)
+{
+	sbitmap_deferred_clear_bit(sb, bitnr);
+
+	if (likely(sb->alloc_hint && !sb->round_robin && bitnr < sb->depth))
+                *this_cpu_ptr(sb->alloc_hint) = bitnr;
+}
+
 static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
 {
 	return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
@@ -368,7 +380,6 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
 {
 	kfree(sbq->ws);
-	free_percpu(sbq->alloc_hint);
 	sbitmap_free(&sbq->sb);
 }
 
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 4e4423414f4d..16f59e99143e 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -9,52 +9,51 @@
 #include <linux/sbitmap.h>
 #include <linux/seq_file.h>
 
-static int init_alloc_hint(struct sbitmap_queue *sbq, gfp_t flags)
+static int init_alloc_hint(struct sbitmap *sb, gfp_t flags)
 {
-	unsigned depth = sbq->sb.depth;
+	unsigned depth = sb->depth;
 
-	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
-	if (!sbq->alloc_hint)
+	sb->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
+	if (!sb->alloc_hint)
 		return -ENOMEM;
 
-	if (depth && !sbq->sb.round_robin) {
+	if (depth && !sb->round_robin) {
 		int i;
 
 		for_each_possible_cpu(i)
-			*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
+			*per_cpu_ptr(sb->alloc_hint, i) = prandom_u32() % depth;
 	}
-
 	return 0;
 }
 
-static inline unsigned update_alloc_hint_before_get(struct sbitmap_queue *sbq,
+static inline unsigned update_alloc_hint_before_get(struct sbitmap *sb,
 						    unsigned int depth)
 {
 	unsigned hint;
 
-	hint = this_cpu_read(*sbq->alloc_hint);
+	hint = this_cpu_read(*sb->alloc_hint);
 	if (unlikely(hint >= depth)) {
 		hint = depth ? prandom_u32() % depth : 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
+		this_cpu_write(*sb->alloc_hint, hint);
 	}
 
 	return hint;
 }
 
-static inline void update_alloc_hint_after_get(struct sbitmap_queue *sbq,
+static inline void update_alloc_hint_after_get(struct sbitmap *sb,
 					       unsigned int depth,
 					       unsigned int hint,
 					       unsigned int nr)
 {
 	if (nr == -1) {
 		/* If the map is full, a hint won't do us much good. */
-		this_cpu_write(*sbq->alloc_hint, 0);
-	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
+		this_cpu_write(*sb->alloc_hint, 0);
+	} else if (nr == hint || unlikely(sb->round_robin)) {
 		/* Only update the hint if we used it. */
 		hint = nr + 1;
 		if (hint >= depth - 1)
 			hint = 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
+		this_cpu_write(*sb->alloc_hint, hint);
 	}
 }
 
@@ -91,7 +90,8 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
 }
 
 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
-		      gfp_t flags, int node, bool round_robin)
+		      gfp_t flags, int node, bool round_robin,
+		      bool alloc_hint)
 {
 	unsigned int bits_per_word;
 	unsigned int i;
@@ -123,9 +123,18 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
 		return 0;
 	}
 
+	if (alloc_hint) {
+		if (init_alloc_hint(sb, flags))
+			return -ENOMEM;
+	} else {
+		sb->alloc_hint = NULL;
+	}
+
 	sb->map = kcalloc_node(sb->map_nr, sizeof(*sb->map), flags, node);
-	if (!sb->map)
+	if (!sb->map) {
+		free_percpu(sb->alloc_hint);
 		return -ENOMEM;
+	}
 
 	for (i = 0; i < sb->map_nr; i++) {
 		sb->map[i].depth = min(depth, bits_per_word);
@@ -204,7 +213,7 @@ static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
 	return nr;
 }
 
-int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
+static int __sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
 {
 	unsigned int i, index;
 	int nr = -1;
@@ -236,10 +245,29 @@ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
 
 	return nr;
 }
+
+int sbitmap_get(struct sbitmap *sb)
+{
+	int nr;
+
+	if (likely(sb->alloc_hint)) {
+		unsigned int hint, depth;
+
+		depth = READ_ONCE(sb->depth);
+		hint = update_alloc_hint_before_get(sb, depth);
+		nr = __sbitmap_get(sb, hint);
+		update_alloc_hint_after_get(sb, depth, hint, nr);
+	} else {
+		nr = __sbitmap_get(sb, 0);
+	}
+
+	return nr;
+}
 EXPORT_SYMBOL_GPL(sbitmap_get);
 
-int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
-			unsigned long shallow_depth)
+static int __sbitmap_get_shallow(struct sbitmap *sb,
+				 unsigned int alloc_hint,
+				 unsigned long shallow_depth)
 {
 	unsigned int i, index;
 	int nr = -1;
@@ -271,6 +299,23 @@ int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
 
 	return nr;
 }
+
+int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth)
+{
+	int nr;
+
+	if (likely(sb->alloc_hint)) {
+		unsigned int hint, depth;
+
+		depth = READ_ONCE(sb->depth);
+		hint = update_alloc_hint_before_get(sb, depth);
+		nr = __sbitmap_get_shallow(sb, hint, shallow_depth);
+		update_alloc_hint_after_get(sb, depth, hint, nr);
+	} else {
+		nr = __sbitmap_get_shallow(sb, 0, shallow_depth);
+	}
+	return nr;
+}
 EXPORT_SYMBOL_GPL(sbitmap_get_shallow);
 
 bool sbitmap_any_bit_set(const struct sbitmap *sb)
@@ -408,15 +453,10 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 	int i;
 
 	ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node,
-				round_robin);
+				round_robin, true);
 	if (ret)
 		return ret;
 
-	if (init_alloc_hint(sbq, flags) != 0) {
-		sbitmap_free(&sbq->sb);
-		return -ENOMEM;
-	}
-
 	sbq->min_shallow_depth = UINT_MAX;
 	sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
 	atomic_set(&sbq->wake_index, 0);
@@ -424,7 +464,6 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 
 	sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
 	if (!sbq->ws) {
-		free_percpu(sbq->alloc_hint);
 		sbitmap_free(&sbq->sb);
 		return -ENOMEM;
 	}
@@ -466,32 +505,16 @@ EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
 
 int __sbitmap_queue_get(struct sbitmap_queue *sbq)
 {
-	unsigned int hint, depth;
-	int nr;
-
-	depth = READ_ONCE(sbq->sb.depth);
-	hint = update_alloc_hint_before_get(sbq, depth);
-	nr = sbitmap_get(&sbq->sb, hint);
-	update_alloc_hint_after_get(sbq, depth, hint, nr);
-
-	return nr;
+	return sbitmap_get(&sbq->sb);
 }
 EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
 
 int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 				unsigned int shallow_depth)
 {
-	unsigned int hint, depth;
-	int nr;
-
 	WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);
 
-	depth = READ_ONCE(sbq->sb.depth);
-	hint = update_alloc_hint_before_get(sbq, depth);
-	nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);
-	update_alloc_hint_after_get(sbq, depth, hint, nr);
-
-	return nr;
+	return sbitmap_get_shallow(&sbq->sb, shallow_depth);
 }
 EXPORT_SYMBOL_GPL(__sbitmap_queue_get_shallow);
 
@@ -600,7 +623,7 @@ void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 	sbitmap_queue_wake_up(sbq);
 
 	if (likely(!sbq->sb.round_robin && nr < sbq->sb.depth))
-		*per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
+		*per_cpu_ptr(sbq->sb.alloc_hint, cpu) = nr;
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
 
@@ -638,7 +661,7 @@ void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
 		if (!first)
 			seq_puts(m, ", ");
 		first = false;
-		seq_printf(m, "%u", *per_cpu_ptr(sbq->alloc_hint, i));
+		seq_printf(m, "%u", *per_cpu_ptr(sbq->sb.alloc_hint, i));
 	}
 	seq_puts(m, "}\n");
 
-- 
2.25.2

[PATCH V3 for 5.11 05/12] sbitmap: export sbitmap_weight

[Ming Lei]

SCSI's .device_busy will be converted to sbitmap, and sbitmap_weight
is needed, so export the helper.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/sbitmap.h |  9 +++++++++
 lib/sbitmap.c           | 11 ++++++-----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index 103b41c03311..34343ce3ef6c 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -346,6 +346,15 @@ static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
  */
 void sbitmap_show(struct sbitmap *sb, struct seq_file *m);
 
+
+/**
+ * sbitmap_weight() - Return how many real bits set in a &struct sbitmap.
+ * @sb: Bitmap to check.
+ *
+ * Return: How many real bits set
+ */
+unsigned int sbitmap_weight(const struct sbitmap *sb);
+
 /**
  * sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct
  * seq_file.
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 16f59e99143e..ab217bf5d619 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -345,20 +345,21 @@ static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set)
 	return weight;
 }
 
-static unsigned int sbitmap_weight(const struct sbitmap *sb)
+static unsigned int sbitmap_cleared(const struct sbitmap *sb)
 {
-	return __sbitmap_weight(sb, true);
+	return __sbitmap_weight(sb, false);
 }
 
-static unsigned int sbitmap_cleared(const struct sbitmap *sb)
+unsigned int sbitmap_weight(const struct sbitmap *sb)
 {
-	return __sbitmap_weight(sb, false);
+	return __sbitmap_weight(sb, true) - sbitmap_cleared(sb);
 }
+EXPORT_SYMBOL_GPL(sbitmap_weight);
 
 void sbitmap_show(struct sbitmap *sb, struct seq_file *m)
 {
 	seq_printf(m, "depth=%u\n", sb->depth);
-	seq_printf(m, "busy=%u\n", sbitmap_weight(sb) - sbitmap_cleared(sb));
+	seq_printf(m, "busy=%u\n", sbitmap_weight(sb));
 	seq_printf(m, "cleared=%u\n", sbitmap_cleared(sb));
 	seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
 	seq_printf(m, "map_nr=%u\n", sb->map_nr);
-- 
2.25.2

[PATCH V3 for 5.11 06/12] sbitmap: add helper of sbitmap_calculate_shift

[Ming Lei]

Move code for calculating default shift into one public helper,
which can be used for SCSI to calculate shift.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/sbitmap.h | 18 ++++++++++++++++++
 lib/sbitmap.c           | 16 +++-------------
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index 34343ce3ef6c..2a40364d6d00 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -337,6 +337,24 @@ static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
 	return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
 }
 
+static inline int sbitmap_calculate_shift(unsigned int depth)
+{
+	int	shift = ilog2(BITS_PER_LONG);
+
+	/*
+	 * If the bitmap is small, shrink the number of bits per word so
+	 * we spread over a few cachelines, at least. If less than 4
+	 * bits, just forget about it, it's not going to work optimally
+	 * anyway.
+	 */
+	if (depth >= 4) {
+		while ((4U << shift) > depth)
+			shift--;
+	}
+
+	return shift;
+}
+
 /**
  * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
  * @sb: Bitmap to show.
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index ab217bf5d619..a428d26aa529 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -96,19 +96,9 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
 	unsigned int bits_per_word;
 	unsigned int i;
 
-	if (shift < 0) {
-		shift = ilog2(BITS_PER_LONG);
-		/*
-		 * If the bitmap is small, shrink the number of bits per word so
-		 * we spread over a few cachelines, at least. If less than 4
-		 * bits, just forget about it, it's not going to work optimally
-		 * anyway.
-		 */
-		if (depth >= 4) {
-			while ((4U << shift) > depth)
-				shift--;
-		}
-	}
+	if (shift < 0)
+		shift = sbitmap_calculate_shift(depth);
+
 	bits_per_word = 1U << shift;
 	if (bits_per_word > BITS_PER_LONG)
 		return -EINVAL;
-- 
2.25.2

[PATCH V3 for 5.11 07/12] blk-mq: add callbacks for storing & retrieving budget token

[Ming Lei]

SCSI is the only driver which requires dispatch budget, and it isn't
fair to add one field into 'struct request' for storing budget token
which will be used in the following patches for improving scsi's device
busy scalability.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/scsi_lib.c  | 18 ++++++++++++++++++
 include/linux/blk-mq.h   |  9 +++++++++
 include/scsi/scsi_cmnd.h |  2 ++
 3 files changed, 29 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0c0548b95e4b..bfcccc73fd01 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1655,6 +1655,20 @@ static bool scsi_mq_get_budget(struct request_queue *q)
 	return false;
 }
 
+static void scsi_mq_set_rq_budget_token(struct request *req, int token)
+{
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
+
+	cmd->budget_token = token;
+}
+
+static int scsi_mq_get_rq_budget_token(struct request *req)
+{
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
+
+	return cmd->budget_token;
+}
+
 static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 			 const struct blk_mq_queue_data *bd)
 {
@@ -1864,6 +1878,8 @@ static const struct blk_mq_ops scsi_mq_ops_no_commit = {
 	.cleanup_rq	= scsi_cleanup_rq,
 	.busy		= scsi_mq_lld_busy,
 	.map_queues	= scsi_map_queues,
+	.set_rq_budget_token = scsi_mq_set_rq_budget_token,
+	.get_rq_budget_token = scsi_mq_get_rq_budget_token,
 };
 
 
@@ -1892,6 +1908,8 @@ static const struct blk_mq_ops scsi_mq_ops = {
 	.cleanup_rq	= scsi_cleanup_rq,
 	.busy		= scsi_mq_lld_busy,
 	.map_queues	= scsi_map_queues,
+	.set_rq_budget_token = scsi_mq_set_rq_budget_token,
+	.get_rq_budget_token = scsi_mq_get_rq_budget_token,
 };
 
 struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev)
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index b23eeca4d677..71060c6a84b1 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -314,6 +314,15 @@ struct blk_mq_ops {
 	 */
 	void (*put_budget)(struct request_queue *);
 
+	/*
+	 * @set_rq_budget_toekn: store rq's budget token
+	 */
+	void (*set_rq_budget_token)(struct request *, int);
+	/*
+	 * @get_rq_budget_toekn: retrieve rq's budget token
+	 */
+	int (*get_rq_budget_token)(struct request *);
+
 	/**
 	 * @timeout: Called on request timeout.
 	 */
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index e76bac4d14c5..b0a2f2ca60ef 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -75,6 +75,8 @@ struct scsi_cmnd {
 
 	int eh_eflags;		/* Used by error handlr */
 
+	int budget_token;
+
 	/*
 	 * This is set to jiffies as it was when the command was first
 	 * allocated.  It is used to time how long the command has
-- 
2.25.2

[PATCH V3 for 5.11 08/12] blk-mq: return budget token from .get_budget callback

[Ming Lei]

SCSI uses one global atomic variable to track queue depth for each
LUN/request queue.

This way doesn't scale well when there is lots of CPU cores and the
disk is very fast. It has been observed that IOPS is affected a lot
by tracking queue depth via sdev->device_busy in IO path.

Return budget token from .get_budget callback, and the budget token
can be passed to driver, so that we can replace the atomic variable
with sbitmap_queue, then the scale issue can be fixed.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq-sched.c    | 17 +++++++++++++----
 block/blk-mq.c          | 36 +++++++++++++++++++++++++-----------
 block/blk-mq.h          | 25 +++++++++++++++++++++----
 drivers/scsi/scsi_lib.c | 16 +++++++++++-----
 include/linux/blk-mq.h  |  4 ++--
 5 files changed, 72 insertions(+), 26 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 3e9596738852..1c04a58c5f99 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -131,6 +131,7 @@ static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
 
 	do {
 		struct request *rq;
+		int budget_token;
 
 		if (e->type->ops.has_work && !e->type->ops.has_work(hctx))
 			break;
@@ -140,12 +141,13 @@ static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
 			break;
 		}
 
-		if (!blk_mq_get_dispatch_budget(q))
+		budget_token = blk_mq_get_dispatch_budget(q);
+		if (budget_token < 0)
 			break;
 
 		rq = e->type->ops.dispatch_request(hctx);
 		if (!rq) {
-			blk_mq_put_dispatch_budget(q);
+			blk_mq_put_dispatch_budget(q, budget_token);
 			/*
 			 * We're releasing without dispatching. Holding the
 			 * budget could have blocked any "hctx"s with the
@@ -157,6 +159,8 @@ static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
 			break;
 		}
 
+		blk_mq_set_rq_budget_token(rq, budget_token);
+
 		/*
 		 * Now this rq owns the budget which has to be released
 		 * if this rq won't be queued to driver via .queue_rq()
@@ -230,6 +234,8 @@ static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
 	struct request *rq;
 
 	do {
+		int budget_token;
+
 		if (!list_empty_careful(&hctx->dispatch)) {
 			ret = -EAGAIN;
 			break;
@@ -238,12 +244,13 @@ static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
 		if (!sbitmap_any_bit_set(&hctx->ctx_map))
 			break;
 
-		if (!blk_mq_get_dispatch_budget(q))
+		budget_token = blk_mq_get_dispatch_budget(q);
+		if (budget_token < 0)
 			break;
 
 		rq = blk_mq_dequeue_from_ctx(hctx, ctx);
 		if (!rq) {
-			blk_mq_put_dispatch_budget(q);
+			blk_mq_put_dispatch_budget(q, budget_token);
 			/*
 			 * We're releasing without dispatching. Holding the
 			 * budget could have blocked any "hctx"s with the
@@ -255,6 +262,8 @@ static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
 			break;
 		}
 
+		blk_mq_set_rq_budget_token(rq, budget_token);
+
 		/*
 		 * Now this rq owns the budget which has to be released
 		 * if this rq won't be queued to driver via .queue_rq()
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 88154cea83d8..7743cacb02b4 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1296,10 +1296,15 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
 						  bool need_budget)
 {
 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+	int budget_token = -1;
 
-	if (need_budget && !blk_mq_get_dispatch_budget(rq->q)) {
-		blk_mq_put_driver_tag(rq);
-		return PREP_DISPATCH_NO_BUDGET;
+	if (need_budget) {
+		budget_token = blk_mq_get_dispatch_budget(rq->q);
+		if (budget_token < 0) {
+			blk_mq_put_driver_tag(rq);
+			return PREP_DISPATCH_NO_BUDGET;
+		}
+		blk_mq_set_rq_budget_token(rq, budget_token);
 	}
 
 	if (!blk_mq_get_driver_tag(rq)) {
@@ -1316,7 +1321,7 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
 			 * together during handling partial dispatch
 			 */
 			if (need_budget)
-				blk_mq_put_dispatch_budget(rq->q);
+				blk_mq_put_dispatch_budget(rq->q, budget_token);
 			return PREP_DISPATCH_NO_TAG;
 		}
 	}
@@ -1326,12 +1331,16 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
 
 /* release all allocated budgets before calling to blk_mq_dispatch_rq_list */
 static void blk_mq_release_budgets(struct request_queue *q,
-		unsigned int nr_budgets)
+		struct list_head *list)
 {
-	int i;
+	struct request *rq;
 
-	for (i = 0; i < nr_budgets; i++)
-		blk_mq_put_dispatch_budget(q);
+	list_for_each_entry(rq, list, queuelist) {
+		int budget_token = blk_mq_get_rq_budget_token(rq);
+
+		if (budget_token >= 0)
+			blk_mq_put_dispatch_budget(q, budget_token);
+	}
 }
 
 /*
@@ -1424,7 +1433,8 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 			(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED);
 		bool no_budget_avail = prep == PREP_DISPATCH_NO_BUDGET;
 
-		blk_mq_release_budgets(q, nr_budgets);
+		if (nr_budgets)
+			blk_mq_release_budgets(q, list);
 
 		/*
 		 * If we didn't flush the entire list, we could have told
@@ -1997,6 +2007,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 {
 	struct request_queue *q = rq->q;
 	bool run_queue = true;
+	int budget_token;
 
 	/*
 	 * RCU or SRCU read lock is needed before checking quiesced flag.
@@ -2014,11 +2025,14 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 	if (q->elevator && !bypass_insert)
 		goto insert;
 
-	if (!blk_mq_get_dispatch_budget(q))
+	budget_token = blk_mq_get_dispatch_budget(q);
+	if (budget_token < 0)
 		goto insert;
 
+	blk_mq_set_rq_budget_token(rq, budget_token);
+
 	if (!blk_mq_get_driver_tag(rq)) {
-		blk_mq_put_dispatch_budget(q);
+		blk_mq_put_dispatch_budget(q, budget_token);
 		goto insert;
 	}
 
diff --git a/block/blk-mq.h b/block/blk-mq.h
index a52703c98b77..bb59a3e54c3b 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -186,17 +186,34 @@ unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part);
 void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
 			 unsigned int inflight[2]);
 
-static inline void blk_mq_put_dispatch_budget(struct request_queue *q)
+static inline void blk_mq_put_dispatch_budget(struct request_queue *q,
+					      int budget_token)
 {
 	if (q->mq_ops->put_budget)
-		q->mq_ops->put_budget(q);
+		q->mq_ops->put_budget(q, budget_token);
 }
 
-static inline bool blk_mq_get_dispatch_budget(struct request_queue *q)
+static inline int blk_mq_get_dispatch_budget(struct request_queue *q)
 {
 	if (q->mq_ops->get_budget)
 		return q->mq_ops->get_budget(q);
-	return true;
+	return 0;
+}
+
+static inline void blk_mq_set_rq_budget_token(struct request *rq, int token)
+{
+	if (token < 0)
+		return;
+
+	if (rq->q->mq_ops->set_rq_budget_token)
+		rq->q->mq_ops->set_rq_budget_token(rq, token);
+}
+
+static inline int blk_mq_get_rq_budget_token(struct request *rq)
+{
+	if (rq->q->mq_ops->get_rq_budget_token)
+		return rq->q->mq_ops->get_rq_budget_token(rq);
+	return -1;
 }
 
 static inline void __blk_mq_inc_active_requests(struct blk_mq_hw_ctx *hctx)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index bfcccc73fd01..41380e200925 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -343,6 +343,7 @@ void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd)
 		atomic_dec(&starget->target_busy);
 
 	atomic_dec(&sdev->device_busy);
+	cmd->budget_token = -1;
 }
 
 static void scsi_kick_queue(struct request_queue *q)
@@ -1128,6 +1129,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 	unsigned long jiffies_at_alloc;
 	int retries, to_clear;
 	bool in_flight;
+	int budget_token = cmd->budget_token;
 
 	if (!blk_rq_is_scsi(rq) && !(flags & SCMD_INITIALIZED)) {
 		flags |= SCMD_INITIALIZED;
@@ -1156,6 +1158,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 	cmd->retries = retries;
 	if (in_flight)
 		__set_bit(SCMD_STATE_INFLIGHT, &cmd->state);
+	cmd->budget_token = budget_token;
 
 }
 
@@ -1618,19 +1621,19 @@ static void scsi_mq_done(struct scsi_cmnd *cmd)
 	blk_mq_complete_request(cmd->request);
 }
 
-static void scsi_mq_put_budget(struct request_queue *q)
+static void scsi_mq_put_budget(struct request_queue *q, int budget_token)
 {
 	struct scsi_device *sdev = q->queuedata;
 
 	atomic_dec(&sdev->device_busy);
 }
 
-static bool scsi_mq_get_budget(struct request_queue *q)
+static int scsi_mq_get_budget(struct request_queue *q)
 {
 	struct scsi_device *sdev = q->queuedata;
 
 	if (scsi_dev_queue_ready(q, sdev))
-		return true;
+		return 0;
 
 	atomic_inc(&sdev->restarts);
 
@@ -1652,7 +1655,7 @@ static bool scsi_mq_get_budget(struct request_queue *q)
 	if (unlikely(atomic_read(&sdev->device_busy) == 0 &&
 				!scsi_device_blocked(sdev)))
 		blk_mq_delay_run_hw_queues(sdev->request_queue, SCSI_QUEUE_DELAY);
-	return false;
+	return -1;
 }
 
 static void scsi_mq_set_rq_budget_token(struct request *req, int token)
@@ -1680,6 +1683,8 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 	blk_status_t ret;
 	int reason;
 
+	WARN_ON_ONCE(cmd->budget_token < 0);
+
 	/*
 	 * If the device is not in running state we will reject some or all
 	 * commands.
@@ -1730,7 +1735,8 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 	if (scsi_target(sdev)->can_queue > 0)
 		atomic_dec(&scsi_target(sdev)->target_busy);
 out_put_budget:
-	scsi_mq_put_budget(q);
+	scsi_mq_put_budget(q, cmd->budget_token);
+	cmd->budget_token = -1;
 	switch (ret) {
 	case BLK_STS_OK:
 		break;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 71060c6a84b1..7b4d4b23403a 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -307,12 +307,12 @@ struct blk_mq_ops {
 	 * reserved budget. Also we have to handle failure case
 	 * of .get_budget for avoiding I/O deadlock.
 	 */
-	bool (*get_budget)(struct request_queue *);
+	int (*get_budget)(struct request_queue *);
 
 	/**
 	 * @put_budget: Release the reserved budget.
 	 */
-	void (*put_budget)(struct request_queue *);
+	void (*put_budget)(struct request_queue *, int);
 
 	/*
 	 * @set_rq_budget_toekn: store rq's budget token
-- 
2.25.2

[PATCH V3 for 5.11 09/12] scsi: put hot fields of scsi_host_template into one cacheline

[Ming Lei]

The following three fields of scsi_host_template are referenced in
scsi IO submission path, so put them together into one cacheline:

- cmd_size
- queuecommand
- commit_rqs

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/scsi/scsi_host.h | 72 ++++++++++++++++++++++------------------
 1 file changed, 39 insertions(+), 33 deletions(-)

diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 46ef8cccc982..6fa2697638b4 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -30,40 +30,15 @@ struct scsi_transport_template;
 #define MODE_TARGET 0x02
 
 struct scsi_host_template {
-	struct module *module;
-	const char *name;
-
 	/*
-	 * The info function will return whatever useful information the
-	 * developer sees fit.  If not provided, then the name field will
-	 * be used instead.
-	 *
-	 * Status: OPTIONAL
+	 * Put fields referenced in IO submission path together in
+	 * same cacheline
 	 */
-	const char *(* info)(struct Scsi_Host *);
 
 	/*
-	 * Ioctl interface
-	 *
-	 * Status: OPTIONAL
-	 */
-	int (*ioctl)(struct scsi_device *dev, unsigned int cmd,
-		     void __user *arg);
-
-
-#ifdef CONFIG_COMPAT
-	/* 
-	 * Compat handler. Handle 32bit ABI.
-	 * When unknown ioctl is passed return -ENOIOCTLCMD.
-	 *
-	 * Status: OPTIONAL
+	 * Additional per-command data allocated for the driver.
 	 */
-	int (*compat_ioctl)(struct scsi_device *dev, unsigned int cmd,
-			    void __user *arg);
-#endif
-
-	int (*init_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
-	int (*exit_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
+	unsigned int cmd_size;
 
 	/*
 	 * The queuecommand function is used to queue up a scsi
@@ -111,6 +86,41 @@ struct scsi_host_template {
 	 */
 	void (*commit_rqs)(struct Scsi_Host *, u16);
 
+	struct module *module;
+	const char *name;
+
+	/*
+	 * The info function will return whatever useful information the
+	 * developer sees fit.  If not provided, then the name field will
+	 * be used instead.
+	 *
+	 * Status: OPTIONAL
+	 */
+	const char *(*info)(struct Scsi_Host *);
+
+	/*
+	 * Ioctl interface
+	 *
+	 * Status: OPTIONAL
+	 */
+	int (*ioctl)(struct scsi_device *dev, unsigned int cmd,
+		     void __user *arg);
+
+
+#ifdef CONFIG_COMPAT
+	/*
+	 * Compat handler. Handle 32bit ABI.
+	 * When unknown ioctl is passed return -ENOIOCTLCMD.
+	 *
+	 * Status: OPTIONAL
+	 */
+	int (*compat_ioctl)(struct scsi_device *dev, unsigned int cmd,
+			    void __user *arg);
+#endif
+
+	int (*init_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
+	int (*exit_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
+
 	/*
 	 * This is an error handling strategy routine.  You don't need to
 	 * define one of these if you don't want to - there is a default
@@ -475,10 +485,6 @@ struct scsi_host_template {
 	 */
 	u64 vendor_id;
 
-	/*
-	 * Additional per-command data allocated for the driver.
-	 */
-	unsigned int cmd_size;
 	struct scsi_host_cmd_pool *cmd_pool;
 
 	/* Delay for runtime autosuspend */
-- 
2.25.2

[PATCH V3 for 5.11 10/12] scsi: add scsi_device_busy() to read sdev->device_busy

[Ming Lei]

Add scsi_device_busy() for drivers, so that we can prepare for tracking
device queue depth via sbitmap_queue.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/message/fusion/mptsas.c      | 2 +-
 drivers/scsi/mpt3sas/mpt3sas_scsih.c | 2 +-
 drivers/scsi/scsi_lib.c              | 4 ++--
 drivers/scsi/scsi_sysfs.c            | 2 +-
 drivers/scsi/sg.c                    | 2 +-
 include/scsi/scsi_device.h           | 5 +++++
 6 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/message/fusion/mptsas.c b/drivers/message/fusion/mptsas.c
index 18b91ea1a353..25dd9b2e12ab 100644
--- a/drivers/message/fusion/mptsas.c
+++ b/drivers/message/fusion/mptsas.c
@@ -3756,7 +3756,7 @@ mptsas_send_link_status_event(struct fw_event_work *fw_event)
 						printk(MYIOC_s_DEBUG_FMT
 						"SDEV OUTSTANDING CMDS"
 						"%d\n", ioc->name,
-						atomic_read(&sdev->device_busy)));
+						scsi_device_busy(sdev)));
 				}
 
 			}
diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index 2e2756d8a49b..cab6e23d8756 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -3060,7 +3060,7 @@ scsih_dev_reset(struct scsi_cmnd *scmd)
 		MPI2_SCSITASKMGMT_TASKTYPE_LOGICAL_UNIT_RESET, 0, 0,
 		tr_timeout, tr_method);
 	/* Check for busy commands after reset */
-	if (r == SUCCESS && atomic_read(&scmd->device->device_busy))
+	if (r == SUCCESS && scsi_device_busy(scmd->device))
 		r = FAILED;
  out:
 	sdev_printk(KERN_INFO, scmd->device, "device reset: %s scmd(0x%p)\n",
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 41380e200925..e5b336847852 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -399,7 +399,7 @@ static void scsi_single_lun_run(struct scsi_device *current_sdev)
 
 static inline bool scsi_device_is_busy(struct scsi_device *sdev)
 {
-	if (atomic_read(&sdev->device_busy) >= sdev->queue_depth)
+	if (scsi_device_busy(sdev) >= sdev->queue_depth)
 		return true;
 	if (atomic_read(&sdev->device_blocked) > 0)
 		return true;
@@ -1652,7 +1652,7 @@ static int scsi_mq_get_budget(struct request_queue *q)
 	 * the .restarts flag, and the request queue will be run for handling
 	 * this request, see scsi_end_request().
 	 */
-	if (unlikely(atomic_read(&sdev->device_busy) == 0 &&
+	if (unlikely(scsi_device_busy(sdev) == 0 &&
 				!scsi_device_blocked(sdev)))
 		blk_mq_delay_run_hw_queues(sdev->request_queue, SCSI_QUEUE_DELAY);
 	return -1;
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 163dbcb741c1..6a51827a4e81 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -659,7 +659,7 @@ sdev_show_device_busy(struct device *dev, struct device_attribute *attr,
 		char *buf)
 {
 	struct scsi_device *sdev = to_scsi_device(dev);
-	return snprintf(buf, 20, "%d\n", atomic_read(&sdev->device_busy));
+	return snprintf(buf, 20, "%d\n", scsi_device_busy(sdev));
 }
 static DEVICE_ATTR(device_busy, S_IRUGO, sdev_show_device_busy, NULL);
 
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 20472aaaf630..8014f504d7b8 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2511,7 +2511,7 @@ static int sg_proc_seq_show_dev(struct seq_file *s, void *v)
 			      scsidp->id, scsidp->lun, (int) scsidp->type,
 			      1,
 			      (int) scsidp->queue_depth,
-			      (int) atomic_read(&scsidp->device_busy),
+			      (int) scsi_device_busy(scsidp),
 			      (int) scsi_device_online(scsidp));
 	}
 	read_unlock_irqrestore(&sg_index_lock, iflags);
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 1a5c9a3df6d6..dd0b9f690a26 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -590,6 +590,11 @@ static inline int scsi_device_supports_vpd(struct scsi_device *sdev)
 	return 0;
 }
 
+static inline int scsi_device_busy(struct scsi_device *sdev)
+{
+	return atomic_read(&sdev->device_busy);
+}
+
 #define MODULE_ALIAS_SCSI_DEVICE(type) \
 	MODULE_ALIAS("scsi:t-" __stringify(type) "*")
 #define SCSI_DEVICE_MODALIAS_FMT "scsi:t-0x%02x"
-- 
2.25.2

[PATCH V3 for 5.11 11/12] scsi: make sure sdev->queue_depth is <= shost->can_queue

[Ming Lei]

Obviously scsi device's queue depth can't be > host's can_queue,
so make it explicitely in scsi_change_queue_depth().

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/scsi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 24619c3bebd5..cc6ff1ae8c16 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -223,6 +223,8 @@ void scsi_finish_command(struct scsi_cmnd *cmd)
  */
 int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
 {
+	depth = min_t(int, depth, sdev->host->can_queue);
+
 	if (depth > 0) {
 		sdev->queue_depth = depth;
 		wmb();
-- 
2.25.2

[PATCH V3 for 5.11 12/12] scsi: replace sdev->device_busy with sbitmap

[Ming Lei]

scsi requires one global atomic variable to track queue depth for each LUN/
request queue, meantime blk-mq tracks queue depth for each hctx. This SCSI's
requirement can't be implemented in blk-mq easily, cause it is a bigger &
harder problem to spread the device or request queue's depth among all hw
queues.

The current approach by using atomic variable can't scale well when there
is lots of CPU cores and the disk is very fast and IO are submitted to this
device concurrently. It has been observed that IOPS is affected a lot by
tracking queue depth via sdev->device_busy in IO path.

So replace the atomic variable sdev->device_busy with sbitmap for
tracking scsi device queue depth.

It is observed that IOPS is improved ~30% by this patchset in the
following test:

1) test machine(32 logical CPU cores)
	Thread(s) per core:  2
	Core(s) per socket:  8
	Socket(s):           2
	NUMA node(s):        2
	Model name:          Intel(R) Xeon(R) Silver 4110 CPU @ 2.10GHz

2) setup scsi_debug:
modprobe scsi_debug virtual_gb=128 max_luns=1 submit_queues=32 delay=0 max_queue=256

3) fio script:
fio --rw=randread --size=128G --direct=1 --ioengine=libaio --iodepth=2048 \
	--numjobs=32 --bs=4k --group_reporting=1 --group_reporting=1 --runtime=60 \
	--loops=10000 --name=job1 --filename=/dev/sdN

[1] https://lore.kernel.org/linux-block/20200119071432.18558-6-ming.lei@redhat.com/

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/scsi.c        |  2 ++
 drivers/scsi/scsi_lib.c    | 33 +++++++++++++++------------------
 drivers/scsi/scsi_priv.h   |  1 +
 drivers/scsi/scsi_scan.c   | 22 ++++++++++++++++++++--
 drivers/scsi/scsi_sysfs.c  |  2 ++
 include/scsi/scsi_device.h |  5 +++--
 6 files changed, 43 insertions(+), 22 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index cc6ff1ae8c16..d0d23d295260 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -233,6 +233,8 @@ int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
 	if (sdev->request_queue)
 		blk_set_queue_depth(sdev->request_queue, depth);
 
+	sbitmap_resize(&sdev->budget_map, sdev->queue_depth);
+
 	return sdev->queue_depth;
 }
 EXPORT_SYMBOL(scsi_change_queue_depth);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e5b336847852..f16bf3118f9a 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -342,7 +342,7 @@ void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd)
 	if (starget->can_queue > 0)
 		atomic_dec(&starget->target_busy);
 
-	atomic_dec(&sdev->device_busy);
+	sbitmap_put(&sdev->budget_map, cmd->budget_token);
 	cmd->budget_token = -1;
 }
 
@@ -1282,19 +1282,17 @@ scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
 }
 
 /*
- * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
- * return 0.
- *
- * Called with the queue_lock held.
+ * scsi_dev_queue_ready: if we can send requests to sdev, assign one token
+ * and return the token else return -1.
  */
 static inline int scsi_dev_queue_ready(struct request_queue *q,
 				  struct scsi_device *sdev)
 {
-	unsigned int busy;
+	int token;
 
-	busy = atomic_inc_return(&sdev->device_busy) - 1;
+	token = sbitmap_get(&sdev->budget_map);
 	if (atomic_read(&sdev->device_blocked)) {
-		if (busy)
+		if (token >= 0)
 			goto out_dec;
 
 		/*
@@ -1306,13 +1304,11 @@ static inline int scsi_dev_queue_ready(struct request_queue *q,
 				   "unblocking device at zero depth\n"));
 	}
 
-	if (busy >= sdev->queue_depth)
-		goto out_dec;
-
-	return 1;
+	return token;
 out_dec:
-	atomic_dec(&sdev->device_busy);
-	return 0;
+	if (token >= 0)
+		sbitmap_put(&sdev->budget_map, token);
+	return -1;
 }
 
 /*
@@ -1625,15 +1621,16 @@ static void scsi_mq_put_budget(struct request_queue *q, int budget_token)
 {
 	struct scsi_device *sdev = q->queuedata;
 
-	atomic_dec(&sdev->device_busy);
+	sbitmap_put(&sdev->budget_map, budget_token);
 }
 
 static int scsi_mq_get_budget(struct request_queue *q)
 {
 	struct scsi_device *sdev = q->queuedata;
+	int token = scsi_dev_queue_ready(q, sdev);
 
-	if (scsi_dev_queue_ready(q, sdev))
-		return 0;
+	if (token >= 0)
+		return token;
 
 	atomic_inc(&sdev->restarts);
 
@@ -1742,7 +1739,7 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 		break;
 	case BLK_STS_RESOURCE:
 	case BLK_STS_ZONE_RESOURCE:
-		if (atomic_read(&sdev->device_busy) ||
+		if (sbitmap_any_bit_set(&sdev->budget_map) ||
 		    scsi_device_blocked(sdev))
 			ret = BLK_STS_DEV_RESOURCE;
 		break;
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index d12ada035961..69145a50a5fa 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -5,6 +5,7 @@
 #include <linux/device.h>
 #include <linux/async.h>
 #include <scsi/scsi_device.h>
+#include <linux/sbitmap.h>
 
 struct request_queue;
 struct request;
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index f2437a7570ce..f674a6ee0a7d 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -215,6 +215,7 @@ static void scsi_unlock_floptical(struct scsi_device *sdev,
 static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
 					   u64 lun, void *hostdata)
 {
+	unsigned int depth;
 	struct scsi_device *sdev;
 	int display_failure_msg = 1, ret;
 	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
@@ -276,8 +277,24 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
 	WARN_ON_ONCE(!blk_get_queue(sdev->request_queue));
 	sdev->request_queue->queuedata = sdev;
 
-	scsi_change_queue_depth(sdev, sdev->host->cmd_per_lun ?
-					sdev->host->cmd_per_lun : 1);
+	depth = sdev->host->cmd_per_lun ?: 1;
+
+	/*
+	 * Use .can_queue as budget map's depth because we have to
+	 * support adjusting queue depth from sysfs. Meantime use
+	 * default device queue depth to figure out sbitmap shift
+	 * since we use this queue depth most of times.
+	 */
+	if (sbitmap_init_node(&sdev->budget_map, sdev->host->can_queue,
+				sbitmap_calculate_shift(depth),
+				GFP_KERNEL, sdev->request_queue->node,
+				false, true)) {
+		put_device(&starget->dev);
+		kfree(sdev);
+		goto out;
+	}
+
+	scsi_change_queue_depth(sdev, depth);
 
 	scsi_sysfs_device_initialize(sdev);
 
@@ -979,6 +996,7 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
 		scsi_attach_vpd(sdev);
 
 	sdev->max_queue_depth = sdev->queue_depth;
+	WARN_ON_ONCE(sdev->max_queue_depth > sdev->budget_map.depth);
 	sdev->sdev_bflags = *bflags;
 
 	/*
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 6a51827a4e81..396b0307d979 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -466,6 +466,8 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 	/* NULL queue means the device can't be used */
 	sdev->request_queue = NULL;
 
+	sbitmap_free(&sdev->budget_map);
+
 	mutex_lock(&sdev->inquiry_mutex);
 	vpd_pg0 = rcu_replace_pointer(sdev->vpd_pg0, vpd_pg0,
 				       lockdep_is_held(&sdev->inquiry_mutex));
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index dd0b9f690a26..05c7c320ef32 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -8,6 +8,7 @@
 #include <linux/blkdev.h>
 #include <scsi/scsi.h>
 #include <linux/atomic.h>
+#include <linux/sbitmap.h>
 
 struct device;
 struct request_queue;
@@ -106,7 +107,7 @@ struct scsi_device {
 	struct list_head    siblings;   /* list of all devices on this host */
 	struct list_head    same_target_siblings; /* just the devices sharing same target id */
 
-	atomic_t device_busy;		/* commands actually active on LLDD */
+	struct sbitmap budget_map;
 	atomic_t device_blocked;	/* Device returned QUEUE_FULL. */
 
 	atomic_t restarts;
@@ -592,7 +593,7 @@ static inline int scsi_device_supports_vpd(struct scsi_device *sdev)
 
 static inline int scsi_device_busy(struct scsi_device *sdev)
 {
-	return atomic_read(&sdev->device_busy);
+	return sbitmap_weight(&sdev->budget_map);
 }
 
 #define MODULE_ALIAS_SCSI_DEVICE(type) \
-- 
2.25.2

Re: [PATCH V3 for 5.11 04/12] sbitmap: move allocation hint into sbitmap

[Hannes Reinecke]

On 9/23/20 3:33 AM, Ming Lei wrote:
> Allocation hint should have belonged to sbitmap, also when sbitmap's
> depth is high and no need to use mulitple wakeup queues, user can
> benefit from percpu allocation hint too.
> 
> So move allocation hint into sbitmap.
> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-mq.c          |   2 +-
>   block/kyber-iosched.c   |   2 +-
>   include/linux/sbitmap.h |  41 ++++++++------
>   lib/sbitmap.c           | 115 ++++++++++++++++++++++++----------------
>   4 files changed, 97 insertions(+), 63 deletions(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 45149970b891..88154cea83d8 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2684,7 +2684,7 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
>   		goto free_cpumask;
>   
>   	if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
> -				gfp, node, false))
> +				gfp, node, false, false))
>   		goto free_ctxs;
>   	hctx->nr_ctx = 0;
>   
> diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
> index cc8bcfe1d587..3949d68ac4c1 100644
> --- a/block/kyber-iosched.c
> +++ b/block/kyber-iosched.c
> @@ -480,7 +480,7 @@ static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
>   	for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
>   		if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
>   				      ilog2(8), GFP_KERNEL, hctx->numa_node,
> -				      false)) {
> +				      false, false)) {
>   			while (--i >= 0)
>   				sbitmap_free(&khd->kcq_map[i]);
>   			goto err_kcqs;
> diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
> index 68097b052ec3..103b41c03311 100644
> --- a/include/linux/sbitmap.h
> +++ b/include/linux/sbitmap.h
> @@ -70,6 +70,14 @@ struct sbitmap {
>   	 * @map: Allocated bitmap.
>   	 */
>   	struct sbitmap_word *map;
> +
> +	/*
> +	 * @alloc_hint: Cache of last successfully allocated or freed bit.
> +	 *
> +	 * This is per-cpu, which allows multiple users to stick to different
> +	 * cachelines until the map is exhausted.
> +	 */
> +	unsigned int __percpu *alloc_hint;
>   };
>   
>   #define SBQ_WAIT_QUEUES 8
> @@ -105,14 +113,6 @@ struct sbitmap_queue {
>   	 */
>   	struct sbitmap sb;
>   
> -	/*
> -	 * @alloc_hint: Cache of last successfully allocated or freed bit.
> -	 *
> -	 * This is per-cpu, which allows multiple users to stick to different
> -	 * cachelines until the map is exhausted.
> -	 */
> -	unsigned int __percpu *alloc_hint;
> -
>   	/**
>   	 * @wake_batch: Number of bits which must be freed before we wake up any
>   	 * waiters.
> @@ -152,11 +152,13 @@ struct sbitmap_queue {
>    * @round_robin: If true, be stricter about allocation order; always allocate
>    *               starting from the last allocated bit. This is less efficient
>    *               than the default behavior (false).
> + * @alloc_hint: If true, apply percpu hint for where to start searching for
> + * 		a free bit.
>    *
>    * Return: Zero on success or negative errno on failure.
>    */
>   int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
> -		      gfp_t flags, int node, bool round_robin);
> +		      gfp_t flags, int node, bool round_robin, bool alloc_hint);
>   
>   /**
>    * sbitmap_free() - Free memory used by a &struct sbitmap.
> @@ -164,6 +166,7 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
>    */
>   static inline void sbitmap_free(struct sbitmap *sb)
>   {
> +	free_percpu(sb->alloc_hint);
>   	kfree(sb->map);
>   	sb->map = NULL;
>   }
> @@ -181,19 +184,17 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth);
>   /**
>    * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
>    * @sb: Bitmap to allocate from.
> - * @alloc_hint: Hint for where to start searching for a free bit.
>    *
>    * This operation provides acquire barrier semantics if it succeeds.
>    *
>    * Return: Non-negative allocated bit number if successful, -1 otherwise.
>    */
> -int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint);
> +int sbitmap_get(struct sbitmap *sb);
>   
>   /**
>    * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
>    * limiting the depth used from each word.
>    * @sb: Bitmap to allocate from.
> - * @alloc_hint: Hint for where to start searching for a free bit.
>    * @shallow_depth: The maximum number of bits to allocate from a single word.
>    *
>    * This rather specific operation allows for having multiple users with
> @@ -205,8 +206,7 @@ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint);
>    *
>    * Return: Non-negative allocated bit number if successful, -1 otherwise.
>    */
> -int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
> -			unsigned long shallow_depth);
> +int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth);
>   
>   /**
>    * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
> @@ -320,6 +320,18 @@ static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int b
>   	set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
>   }
>   
> +/*
> + * Pair of sbitmap_get, and this one applies both cleared bit and
> + * allocation hint.
> + */
> +static inline void sbitmap_put(struct sbitmap *sb, unsigned int bitnr)
> +{
> +	sbitmap_deferred_clear_bit(sb, bitnr);
> +
> +	if (likely(sb->alloc_hint && !sb->round_robin && bitnr < sb->depth))
> +                *this_cpu_ptr(sb->alloc_hint) = bitnr;
> +}
> +
>   static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
>   {
>   	return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
> @@ -368,7 +380,6 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
>   static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
>   {
>   	kfree(sbq->ws);
> -	free_percpu(sbq->alloc_hint);
>   	sbitmap_free(&sbq->sb);
>   }
>   
> diff --git a/lib/sbitmap.c b/lib/sbitmap.c
> index 4e4423414f4d..16f59e99143e 100644
> --- a/lib/sbitmap.c
> +++ b/lib/sbitmap.c
> @@ -9,52 +9,51 @@
>   #include <linux/sbitmap.h>
>   #include <linux/seq_file.h>
>   
> -static int init_alloc_hint(struct sbitmap_queue *sbq, gfp_t flags)
> +static int init_alloc_hint(struct sbitmap *sb, gfp_t flags)
>   {
> -	unsigned depth = sbq->sb.depth;
> +	unsigned depth = sb->depth;
>   
> -	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
> -	if (!sbq->alloc_hint)
> +	sb->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
> +	if (!sb->alloc_hint)
>   		return -ENOMEM;
>   
> -	if (depth && !sbq->sb.round_robin) {
> +	if (depth && !sb->round_robin) {
>   		int i;
>   
>   		for_each_possible_cpu(i)
> -			*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
> +			*per_cpu_ptr(sb->alloc_hint, i) = prandom_u32() % depth;
>   	}
> -
>   	return 0;
>   }
>   
> -static inline unsigned update_alloc_hint_before_get(struct sbitmap_queue *sbq,
> +static inline unsigned update_alloc_hint_before_get(struct sbitmap *sb,
>   						    unsigned int depth)
>   {
>   	unsigned hint;
>   
> -	hint = this_cpu_read(*sbq->alloc_hint);
> +	hint = this_cpu_read(*sb->alloc_hint);
>   	if (unlikely(hint >= depth)) {
>   		hint = depth ? prandom_u32() % depth : 0;
> -		this_cpu_write(*sbq->alloc_hint, hint);
> +		this_cpu_write(*sb->alloc_hint, hint);
>   	}
>   
>   	return hint;
>   }
>   
> -static inline void update_alloc_hint_after_get(struct sbitmap_queue *sbq,
> +static inline void update_alloc_hint_after_get(struct sbitmap *sb,
>   					       unsigned int depth,
>   					       unsigned int hint,
>   					       unsigned int nr)
>   {
>   	if (nr == -1) {
>   		/* If the map is full, a hint won't do us much good. */
> -		this_cpu_write(*sbq->alloc_hint, 0);
> -	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
> +		this_cpu_write(*sb->alloc_hint, 0);
> +	} else if (nr == hint || unlikely(sb->round_robin)) {
>   		/* Only update the hint if we used it. */
>   		hint = nr + 1;
>   		if (hint >= depth - 1)
>   			hint = 0;
> -		this_cpu_write(*sbq->alloc_hint, hint);
> +		this_cpu_write(*sb->alloc_hint, hint);
>   	}
>   }
>   
> @@ -91,7 +90,8 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
>   }
>   
>   int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
> -		      gfp_t flags, int node, bool round_robin)
> +		      gfp_t flags, int node, bool round_robin,
> +		      bool alloc_hint)
>   {
>   	unsigned int bits_per_word;
>   	unsigned int i;
> @@ -123,9 +123,18 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
>   		return 0;
>   	}
>   
> +	if (alloc_hint) {
> +		if (init_alloc_hint(sb, flags))
> +			return -ENOMEM;
> +	} else {
> +		sb->alloc_hint = NULL;
> +	}
> +
>   	sb->map = kcalloc_node(sb->map_nr, sizeof(*sb->map), flags, node);
> -	if (!sb->map)
> +	if (!sb->map) {
> +		free_percpu(sb->alloc_hint);
>   		return -ENOMEM;
> +	}
>   
>   	for (i = 0; i < sb->map_nr; i++) {
>   		sb->map[i].depth = min(depth, bits_per_word);
> @@ -204,7 +213,7 @@ static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
>   	return nr;
>   }
>   
> -int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
> +static int __sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
>   {
>   	unsigned int i, index;
>   	int nr = -1;
> @@ -236,10 +245,29 @@ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
>   
>   	return nr;
>   }
> +
> +int sbitmap_get(struct sbitmap *sb)
> +{
> +	int nr;
> +
> +	if (likely(sb->alloc_hint)) {
> +		unsigned int hint, depth;
> +
> +		depth = READ_ONCE(sb->depth);
> +		hint = update_alloc_hint_before_get(sb, depth);
> +		nr = __sbitmap_get(sb, hint);
> +		update_alloc_hint_after_get(sb, depth, hint, nr);
> +	} else {
> +		nr = __sbitmap_get(sb, 0);
> +	}
> +
> +	return nr;
> +}
>   EXPORT_SYMBOL_GPL(sbitmap_get);
>   
Can't you move the 'alloc_hint' test into update_alloc_hint_before_get()?
That way we can simplify the code and would avoid the 'if' clause here.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH V3 for 5.11 05/12] sbitmap: export sbitmap_weight

[Hannes Reinecke]

On 9/23/20 3:33 AM, Ming Lei wrote:
> SCSI's .device_busy will be converted to sbitmap, and sbitmap_weight
> is needed, so export the helper.
> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   include/linux/sbitmap.h |  9 +++++++++
>   lib/sbitmap.c           | 11 ++++++-----
>   2 files changed, 15 insertions(+), 5 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH V3 for 5.11 06/12] sbitmap: add helper of sbitmap_calculate_shift

[Hannes Reinecke]

On 9/23/20 3:33 AM, Ming Lei wrote:
> Move code for calculating default shift into one public helper,
> which can be used for SCSI to calculate shift.
> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   include/linux/sbitmap.h | 18 ++++++++++++++++++
>   lib/sbitmap.c           | 16 +++-------------
>   2 files changed, 21 insertions(+), 13 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH V3 for 5.11 07/12] blk-mq: add callbacks for storing & retrieving budget token

[Hannes Reinecke]

On 9/23/20 3:33 AM, Ming Lei wrote:
> SCSI is the only driver which requires dispatch budget, and it isn't
> fair to add one field into 'struct request' for storing budget token
> which will be used in the following patches for improving scsi's device
> busy scalability.
> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   drivers/scsi/scsi_lib.c  | 18 ++++++++++++++++++
>   include/linux/blk-mq.h   |  9 +++++++++
>   include/scsi/scsi_cmnd.h |  2 ++
>   3 files changed, 29 insertions(+)
>Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH V3 for 5.11 08/12] blk-mq: return budget token from .get_budget callback

[Hannes Reinecke]

On 9/23/20 3:33 AM, Ming Lei wrote:
> SCSI uses one global atomic variable to track queue depth for each
> LUN/request queue.
> 
> This way doesn't scale well when there is lots of CPU cores and the
> disk is very fast. It has been observed that IOPS is affected a lot
> by tracking queue depth via sdev->device_busy in IO path.
> 
> Return budget token from .get_budget callback, and the budget token
> can be passed to driver, so that we can replace the atomic variable
> with sbitmap_queue, then the scale issue can be fixed.
> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-mq-sched.c    | 17 +++++++++++++----
>   block/blk-mq.c          | 36 +++++++++++++++++++++++++-----------
>   block/blk-mq.h          | 25 +++++++++++++++++++++----
>   drivers/scsi/scsi_lib.c | 16 +++++++++++-----
>   include/linux/blk-mq.h  |  4 ++--
>   5 files changed, 72 insertions(+), 26 deletions(-)
> 
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index 3e9596738852..1c04a58c5f99 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -131,6 +131,7 @@ static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
>   
>   	do {
>   		struct request *rq;
> +		int budget_token;
>   
>   		if (e->type->ops.has_work && !e->type->ops.has_work(hctx))
>   			break;
> @@ -140,12 +141,13 @@ static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
>   			break;
>   		}
>   
> -		if (!blk_mq_get_dispatch_budget(q))
> +		budget_token = blk_mq_get_dispatch_budget(q);
> +		if (budget_token < 0)
>   			break;
>   
>   		rq = e->type->ops.dispatch_request(hctx);
>   		if (!rq) {
> -			blk_mq_put_dispatch_budget(q);
> +			blk_mq_put_dispatch_budget(q, budget_token);
>   			/*
>   			 * We're releasing without dispatching. Holding the
>   			 * budget could have blocked any "hctx"s with the
> @@ -157,6 +159,8 @@ static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
>   			break;
>   		}
>   
> +		blk_mq_set_rq_budget_token(rq, budget_token);
> +
>   		/*
>   		 * Now this rq owns the budget which has to be released
>   		 * if this rq won't be queued to driver via .queue_rq()
> @@ -230,6 +234,8 @@ static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
>   	struct request *rq;
>   
>   	do {
> +		int budget_token;
> +
>   		if (!list_empty_careful(&hctx->dispatch)) {
>   			ret = -EAGAIN;
>   			break;
> @@ -238,12 +244,13 @@ static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
>   		if (!sbitmap_any_bit_set(&hctx->ctx_map))
>   			break;
>   
> -		if (!blk_mq_get_dispatch_budget(q))
> +		budget_token = blk_mq_get_dispatch_budget(q);
> +		if (budget_token < 0)
>   			break;
>   
>   		rq = blk_mq_dequeue_from_ctx(hctx, ctx);
>   		if (!rq) {
> -			blk_mq_put_dispatch_budget(q);
> +			blk_mq_put_dispatch_budget(q, budget_token);
>   			/*
>   			 * We're releasing without dispatching. Holding the
>   			 * budget could have blocked any "hctx"s with the
> @@ -255,6 +262,8 @@ static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
>   			break;
>   		}
>   
> +		blk_mq_set_rq_budget_token(rq, budget_token);
> +
>   		/*
>   		 * Now this rq owns the budget which has to be released
>   		 * if this rq won't be queued to driver via .queue_rq()
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 88154cea83d8..7743cacb02b4 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1296,10 +1296,15 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
>   						  bool need_budget)
>   {
>   	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
> +	int budget_token = -1;
>   
> -	if (need_budget && !blk_mq_get_dispatch_budget(rq->q)) {
> -		blk_mq_put_driver_tag(rq);
> -		return PREP_DISPATCH_NO_BUDGET;
> +	if (need_budget) {
> +		budget_token = blk_mq_get_dispatch_budget(rq->q);
> +		if (budget_token < 0) {
> +			blk_mq_put_driver_tag(rq);
> +			return PREP_DISPATCH_NO_BUDGET;
> +		}
> +		blk_mq_set_rq_budget_token(rq, budget_token);
>   	}
>   
>   	if (!blk_mq_get_driver_tag(rq)) {
> @@ -1316,7 +1321,7 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
>   			 * together during handling partial dispatch
>   			 */
>   			if (need_budget)
> -				blk_mq_put_dispatch_budget(rq->q);
> +				blk_mq_put_dispatch_budget(rq->q, budget_token);
>   			return PREP_DISPATCH_NO_TAG;
>   		}
>   	}
> @@ -1326,12 +1331,16 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
>   
>   /* release all allocated budgets before calling to blk_mq_dispatch_rq_list */
>   static void blk_mq_release_budgets(struct request_queue *q,
> -		unsigned int nr_budgets)
> +		struct list_head *list)
>   {
> -	int i;
> +	struct request *rq;
>   
> -	for (i = 0; i < nr_budgets; i++)
> -		blk_mq_put_dispatch_budget(q);
> +	list_for_each_entry(rq, list, queuelist) {
> +		int budget_token = blk_mq_get_rq_budget_token(rq);
> +
> +		if (budget_token >= 0)
> +			blk_mq_put_dispatch_budget(q, budget_token);
> +	}
>   }
>   
>   /*
> @@ -1424,7 +1433,8 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
>   			(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED);
>   		bool no_budget_avail = prep == PREP_DISPATCH_NO_BUDGET;
>   
> -		blk_mq_release_budgets(q, nr_budgets);
> +		if (nr_budgets)
> +			blk_mq_release_budgets(q, list);
>   
>   		/*
>   		 * If we didn't flush the entire list, we could have told
> @@ -1997,6 +2007,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
>   {
>   	struct request_queue *q = rq->q;
>   	bool run_queue = true;
> +	int budget_token;
>   
>   	/*
>   	 * RCU or SRCU read lock is needed before checking quiesced flag.
> @@ -2014,11 +2025,14 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
>   	if (q->elevator && !bypass_insert)
>   		goto insert;
>   
> -	if (!blk_mq_get_dispatch_budget(q))
> +	budget_token = blk_mq_get_dispatch_budget(q);
> +	if (budget_token < 0)
>   		goto insert;
>   
> +	blk_mq_set_rq_budget_token(rq, budget_token);
> +
>   	if (!blk_mq_get_driver_tag(rq)) {
> -		blk_mq_put_dispatch_budget(q);
> +		blk_mq_put_dispatch_budget(q, budget_token);
>   		goto insert;
>   	}
>   
> diff --git a/block/blk-mq.h b/block/blk-mq.h
> index a52703c98b77..bb59a3e54c3b 100644
> --- a/block/blk-mq.h
> +++ b/block/blk-mq.h
> @@ -186,17 +186,34 @@ unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part);
>   void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
>   			 unsigned int inflight[2]);
>   
> -static inline void blk_mq_put_dispatch_budget(struct request_queue *q)
> +static inline void blk_mq_put_dispatch_budget(struct request_queue *q,
> +					      int budget_token)
>   {
>   	if (q->mq_ops->put_budget)
> -		q->mq_ops->put_budget(q);
> +		q->mq_ops->put_budget(q, budget_token);
>   }
>   
> -static inline bool blk_mq_get_dispatch_budget(struct request_queue *q)
> +static inline int blk_mq_get_dispatch_budget(struct request_queue *q)
>   {
>   	if (q->mq_ops->get_budget)
>   		return q->mq_ops->get_budget(q);
> -	return true;
> +	return 0;
> +}
> +
> +static inline void blk_mq_set_rq_budget_token(struct request *rq, int token)
> +{
> +	if (token < 0)
> +		return;
> +
> +	if (rq->q->mq_ops->set_rq_budget_token)
> +		rq->q->mq_ops->set_rq_budget_token(rq, token);
> +}
> +
> +static inline int blk_mq_get_rq_budget_token(struct request *rq)
> +{
> +	if (rq->q->mq_ops->get_rq_budget_token)
> +		return rq->q->mq_ops->get_rq_budget_token(rq);
> +	return -1;
>   }
>   
>   static inline void __blk_mq_inc_active_requests(struct blk_mq_hw_ctx *hctx)
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index bfcccc73fd01..41380e200925 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -343,6 +343,7 @@ void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd)
>   		atomic_dec(&starget->target_busy);
>   
>   	atomic_dec(&sdev->device_busy);
> +	cmd->budget_token = -1;
>   }
>   
>   static void scsi_kick_queue(struct request_queue *q)
> @@ -1128,6 +1129,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
>   	unsigned long jiffies_at_alloc;
>   	int retries, to_clear;
>   	bool in_flight;
> +	int budget_token = cmd->budget_token;
>   
>   	if (!blk_rq_is_scsi(rq) && !(flags & SCMD_INITIALIZED)) {
>   		flags |= SCMD_INITIALIZED;
> @@ -1156,6 +1158,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
>   	cmd->retries = retries;
>   	if (in_flight)
>   		__set_bit(SCMD_STATE_INFLIGHT, &cmd->state);
> +	cmd->budget_token = budget_token;
>   
>   }
>   
> @@ -1618,19 +1621,19 @@ static void scsi_mq_done(struct scsi_cmnd *cmd)
>   	blk_mq_complete_request(cmd->request);
>   }
>   
> -static void scsi_mq_put_budget(struct request_queue *q)
> +static void scsi_mq_put_budget(struct request_queue *q, int budget_token)
>   {
>   	struct scsi_device *sdev = q->queuedata;
>   
>   	atomic_dec(&sdev->device_busy);
>   }
>   
> -static bool scsi_mq_get_budget(struct request_queue *q)
> +static int scsi_mq_get_budget(struct request_queue *q)
>   {
>   	struct scsi_device *sdev = q->queuedata;
>   
>   	if (scsi_dev_queue_ready(q, sdev))
> -		return true;
> +		return 0;
>   
>   	atomic_inc(&sdev->restarts);
>   
> @@ -1652,7 +1655,7 @@ static bool scsi_mq_get_budget(struct request_queue *q)
>   	if (unlikely(atomic_read(&sdev->device_busy) == 0 &&
>   				!scsi_device_blocked(sdev)))
>   		blk_mq_delay_run_hw_queues(sdev->request_queue, SCSI_QUEUE_DELAY);
> -	return false;
> +	return -1;
>   }
>   
>   static void scsi_mq_set_rq_budget_token(struct request *req, int token)
> @@ -1680,6 +1683,8 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
>   	blk_status_t ret;
>   	int reason;
>   
> +	WARN_ON_ONCE(cmd->budget_token < 0);
> +
>   	/*
>   	 * If the device is not in running state we will reject some or all
>   	 * commands.
> @@ -1730,7 +1735,8 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
>   	if (scsi_target(sdev)->can_queue > 0)
>   		atomic_dec(&scsi_target(sdev)->target_busy);
>   out_put_budget:
> -	scsi_mq_put_budget(q);
> +	scsi_mq_put_budget(q, cmd->budget_token);
> +	cmd->budget_token = -1;
>   	switch (ret) {
>   	case BLK_STS_OK:
>   		break;
> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
> index 71060c6a84b1..7b4d4b23403a 100644
> --- a/include/linux/blk-mq.h
> +++ b/include/linux/blk-mq.h
> @@ -307,12 +307,12 @@ struct blk_mq_ops {
>   	 * reserved budget. Also we have to handle failure case
>   	 * of .get_budget for avoiding I/O deadlock.
>   	 */
> -	bool (*get_budget)(struct request_queue *);
> +	int (*get_budget)(struct request_queue *);
>   
>   	/**
>   	 * @put_budget: Release the reserved budget.
>   	 */
> -	void (*put_budget)(struct request_queue *);
> +	void (*put_budget)(struct request_queue *, int);
>   
>   	/*
>   	 * @set_rq_budget_toekn: store rq's budget token
> 
In principle, yes. But I would like to have some more clarification 
about the values the 'budget_token' can have.
 From what I gather -1 means 'no budget', but what exactly is the 
difference between '0' and, say, '5'?
And indeed I would prefer to have the budget token to be unsigned,
such that '0' means 'no budget', and any positive number would indicate 
the budget itself.
Can we have a bit more documentation here?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH V3 for 5.11 09/12] scsi: put hot fields of scsi_host_template into one cacheline

[Hannes Reinecke]

On 9/23/20 3:33 AM, Ming Lei wrote:
> The following three fields of scsi_host_template are referenced in
> scsi IO submission path, so put them together into one cacheline:
> 
> - cmd_size
> - queuecommand
> - commit_rqs
> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   include/scsi/scsi_host.h | 72 ++++++++++++++++++++++------------------
>   1 file changed, 39 insertions(+), 33 deletions(-)
> Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH V3 for 5.11 10/12] scsi: add scsi_device_busy() to read sdev->device_busy

[Hannes Reinecke]

On 9/23/20 3:33 AM, Ming Lei wrote:
> Add scsi_device_busy() for drivers, so that we can prepare for tracking
> device queue depth via sbitmap_queue.
> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   drivers/message/fusion/mptsas.c      | 2 +-
>   drivers/scsi/mpt3sas/mpt3sas_scsih.c | 2 +-
>   drivers/scsi/scsi_lib.c              | 4 ++--
>   drivers/scsi/scsi_sysfs.c            | 2 +-
>   drivers/scsi/sg.c                    | 2 +-
>   include/scsi/scsi_device.h           | 5 +++++
>   6 files changed, 11 insertions(+), 6 deletions(-)
> Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH V3 for 5.11 11/12] scsi: make sure sdev->queue_depth is <= shost->can_queue

[Hannes Reinecke]

On 9/23/20 3:33 AM, Ming Lei wrote:
> Obviously scsi device's queue depth can't be > host's can_queue,
> so make it explicitely in scsi_change_queue_depth().
> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   drivers/scsi/scsi.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> index 24619c3bebd5..cc6ff1ae8c16 100644
> --- a/drivers/scsi/scsi.c
> +++ b/drivers/scsi/scsi.c
> @@ -223,6 +223,8 @@ void scsi_finish_command(struct scsi_cmnd *cmd)
>    */
>   int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
>   {
> +	depth = min_t(int, depth, sdev->host->can_queue);
> +
>   	if (depth > 0) {
>   		sdev->queue_depth = depth;
>   		wmb();
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH V3 for 5.11 12/12] scsi: replace sdev->device_busy with sbitmap

[Hannes Reinecke]

On 9/23/20 3:33 AM, Ming Lei wrote:
> scsi requires one global atomic variable to track queue depth for each LUN/
> request queue, meantime blk-mq tracks queue depth for each hctx. This SCSI's
> requirement can't be implemented in blk-mq easily, cause it is a bigger &
> harder problem to spread the device or request queue's depth among all hw
> queues.
> 
> The current approach by using atomic variable can't scale well when there
> is lots of CPU cores and the disk is very fast and IO are submitted to this
> device concurrently. It has been observed that IOPS is affected a lot by
> tracking queue depth via sdev->device_busy in IO path.
> 
> So replace the atomic variable sdev->device_busy with sbitmap for
> tracking scsi device queue depth.
> 
> It is observed that IOPS is improved ~30% by this patchset in the
> following test:
> 
> 1) test machine(32 logical CPU cores)
> 	Thread(s) per core:  2
> 	Core(s) per socket:  8
> 	Socket(s):           2
> 	NUMA node(s):        2
> 	Model name:          Intel(R) Xeon(R) Silver 4110 CPU @ 2.10GHz
> 
> 2) setup scsi_debug:
> modprobe scsi_debug virtual_gb=128 max_luns=1 submit_queues=32 delay=0 max_queue=256
> 
> 3) fio script:
> fio --rw=randread --size=128G --direct=1 --ioengine=libaio --iodepth=2048 \
> 	--numjobs=32 --bs=4k --group_reporting=1 --group_reporting=1 --runtime=60 \
> 	--loops=10000 --name=job1 --filename=/dev/sdN
> 
> [1] https://lore.kernel.org/linux-block/20200119071432.18558-6-ming.lei@redhat.com/
> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   drivers/scsi/scsi.c        |  2 ++
>   drivers/scsi/scsi_lib.c    | 33 +++++++++++++++------------------
>   drivers/scsi/scsi_priv.h   |  1 +
>   drivers/scsi/scsi_scan.c   | 22 ++++++++++++++++++++--
>   drivers/scsi/scsi_sysfs.c  |  2 ++
>   include/scsi/scsi_device.h |  5 +++--
>   6 files changed, 43 insertions(+), 22 deletions(-)
> 
Ah. Now it makes sense why 'no budget' has been set to -1.
Ok.

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH V3 for 5.11 11/12] scsi: make sure sdev->queue_depth is <= shost->can_queue

[John Garry]

On 23/09/2020 02:33, Ming Lei wrote:
> Obviously scsi device's queue depth can't be > host's can_queue,
> so make it explicitely in scsi_change_queue_depth().

ha, why not can_queue * nr_hw_queues?

> 
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   drivers/scsi/scsi.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> index 24619c3bebd5..cc6ff1ae8c16 100644
> --- a/drivers/scsi/scsi.c
> +++ b/drivers/scsi/scsi.c
> @@ -223,6 +223,8 @@ void scsi_finish_command(struct scsi_cmnd *cmd)
>    */
>   int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
>   {
> +	depth = min_t(int, depth, sdev->host->can_queue);
> +
>   	if (depth > 0) {
>   		sdev->queue_depth = depth;
>   		wmb();
> 

Re: [PATCH V3 for 5.11 01/12] sbitmap: remove sbitmap_clear_bit_unlock

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

Re: [PATCH V3 for 5.11 00/12] blk-mq/scsi: tracking device queue depth via sbitmap

[Sumanesh Samanta]

[-- Attachment #1: Type: text/plain, Size: 4266 bytes --]

Hi Ming,

I have tested this patch extensively in our labs.

This patch gives excellent results when a single device can provide
very high IOPs, and only a few of those devices are available on the
system.
Thus, if a RAID 0 volume is created out of many high end NVMe devices,
then that RAID0 volume can potentially reach a max IOPs that is a
summation of the maxs IOPS for all the underlying drives. Without this
patch, the current kernel code cannot get there.

For example, for a simple RAID0 volume with 32 NVMe drives, I got
almost 100% performance boost with this patch.
The NVMe stack does not have this limitation, and this patch goes a
long way in closing that gap.

I have also tested it in many other configurations, and  did not see
any adverse side effects.

Please feel free to add:
Tested-by: Sumanesh Samanta

Thanks,
Sumanesh




On Tue, Sep 22, 2020 at 7:33 PM Ming Lei <ming.lei@redhat.com> wrote:
>
> Hi,
>
> scsi uses one global atomic variable to track queue depth for each
> LUN/request queue. This way can't scale well when there is lots of CPU
> cores and the disk is very fast. Broadcom guys has complained that their
> high end HBA can't reach top performance because .device_busy is
> operated in IO path.
>
> Replace the atomic variable sdev->device_busy with sbitmap for
> tracking scsi device queue depth.
>
> Test on scsi_debug shows this way improve IOPS > 20%. Meantime
> the IOPS difference is just ~1% compared with bypassing .device_busy
> on scsi_debug via patches[1]
>
> The 1st 6 patches moves percpu allocation hint into sbitmap, since
> the improvement by doing percpu allocation hint on sbitmap is observable.
> Meantime export helpers for SCSI.
>
> Patch 7 and 8 prepares for the conversion by returning budget token
> from .get_budget callback, meantime passes the budget token to driver
> via 'struct blk_mq_queue_data' in .queue_rq().
>
> The last four patches changes SCSI for switching to track device queue
> depth via sbitmap.
>
> The patchset have been tested by Broadcom, and obvious performance boost
> can be observed.
>
> Given it is based on both for-5.10/block and 5.10/scsi-queue, the target
> is for v5.11. And it is posted out just for getting full/enough review.
>
> Please comment and review!
>
> V3:
>         - rebase on both for-5.10/block and 5.10/scsi-queue.
>
> V2:
>         - fix one build failure
>
>
> Ming Lei (12):
>   sbitmap: remove sbitmap_clear_bit_unlock
>   sbitmap: maintain allocation round_robin in sbitmap
>   sbitmap: add helpers for updating allocation hint
>   sbitmap: move allocation hint into sbitmap
>   sbitmap: export sbitmap_weight
>   sbitmap: add helper of sbitmap_calculate_shift
>   blk-mq: add callbacks for storing & retrieving budget token
>   blk-mq: return budget token from .get_budget callback
>   scsi: put hot fields of scsi_host_template into one cacheline
>   scsi: add scsi_device_busy() to read sdev->device_busy
>   scsi: make sure sdev->queue_depth is <= shost->can_queue
>   scsi: replace sdev->device_busy with sbitmap
>
>  block/blk-mq-sched.c                 |  17 ++-
>  block/blk-mq.c                       |  38 +++--
>  block/blk-mq.h                       |  25 +++-
>  block/kyber-iosched.c                |   3 +-
>  drivers/message/fusion/mptsas.c      |   2 +-
>  drivers/scsi/mpt3sas/mpt3sas_scsih.c |   2 +-
>  drivers/scsi/scsi.c                  |   4 +
>  drivers/scsi/scsi_lib.c              |  69 ++++++---
>  drivers/scsi/scsi_priv.h             |   1 +
>  drivers/scsi/scsi_scan.c             |  22 ++-
>  drivers/scsi/scsi_sysfs.c            |   4 +-
>  drivers/scsi/sg.c                    |   2 +-
>  include/linux/blk-mq.h               |  13 +-
>  include/linux/sbitmap.h              |  84 +++++++----
>  include/scsi/scsi_cmnd.h             |   2 +
>  include/scsi/scsi_device.h           |   8 +-
>  include/scsi/scsi_host.h             |  72 ++++-----
>  lib/sbitmap.c                        | 213 +++++++++++++++------------
>  18 files changed, 376 insertions(+), 205 deletions(-)
>
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> Cc: Ewan D. Milne <emilne@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
>
> --
> 2.25.2
>

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Re: [PATCH V3 for 5.11 04/12] sbitmap: move allocation hint into sbitmap

[Ming Lei]

On Wed, Sep 23, 2020 at 08:36:42AM +0200, Hannes Reinecke wrote:
> On 9/23/20 3:33 AM, Ming Lei wrote:
> > Allocation hint should have belonged to sbitmap, also when sbitmap's
> > depth is high and no need to use mulitple wakeup queues, user can
> > benefit from percpu allocation hint too.
> > 
> > So move allocation hint into sbitmap.
> > 
> > Cc: Omar Sandoval <osandov@fb.com>
> > Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> > Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
> > Cc: Ewan D. Milne <emilne@redhat.com>
> > Cc: Hannes Reinecke <hare@suse.de>
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> >   block/blk-mq.c          |   2 +-
> >   block/kyber-iosched.c   |   2 +-
> >   include/linux/sbitmap.h |  41 ++++++++------
> >   lib/sbitmap.c           | 115 ++++++++++++++++++++++++----------------
> >   4 files changed, 97 insertions(+), 63 deletions(-)
> > 
> > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > index 45149970b891..88154cea83d8 100644
> > --- a/block/blk-mq.c
> > +++ b/block/blk-mq.c
> > @@ -2684,7 +2684,7 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
> >   		goto free_cpumask;
> >   	if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
> > -				gfp, node, false))
> > +				gfp, node, false, false))
> >   		goto free_ctxs;
> >   	hctx->nr_ctx = 0;
> > diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
> > index cc8bcfe1d587..3949d68ac4c1 100644
> > --- a/block/kyber-iosched.c
> > +++ b/block/kyber-iosched.c
> > @@ -480,7 +480,7 @@ static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
> >   	for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
> >   		if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
> >   				      ilog2(8), GFP_KERNEL, hctx->numa_node,
> > -				      false)) {
> > +				      false, false)) {
> >   			while (--i >= 0)
> >   				sbitmap_free(&khd->kcq_map[i]);
> >   			goto err_kcqs;
> > diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
> > index 68097b052ec3..103b41c03311 100644
> > --- a/include/linux/sbitmap.h
> > +++ b/include/linux/sbitmap.h
> > @@ -70,6 +70,14 @@ struct sbitmap {
> >   	 * @map: Allocated bitmap.
> >   	 */
> >   	struct sbitmap_word *map;
> > +
> > +	/*
> > +	 * @alloc_hint: Cache of last successfully allocated or freed bit.
> > +	 *
> > +	 * This is per-cpu, which allows multiple users to stick to different
> > +	 * cachelines until the map is exhausted.
> > +	 */
> > +	unsigned int __percpu *alloc_hint;
> >   };
> >   #define SBQ_WAIT_QUEUES 8
> > @@ -105,14 +113,6 @@ struct sbitmap_queue {
> >   	 */
> >   	struct sbitmap sb;
> > -	/*
> > -	 * @alloc_hint: Cache of last successfully allocated or freed bit.
> > -	 *
> > -	 * This is per-cpu, which allows multiple users to stick to different
> > -	 * cachelines until the map is exhausted.
> > -	 */
> > -	unsigned int __percpu *alloc_hint;
> > -
> >   	/**
> >   	 * @wake_batch: Number of bits which must be freed before we wake up any
> >   	 * waiters.
> > @@ -152,11 +152,13 @@ struct sbitmap_queue {
> >    * @round_robin: If true, be stricter about allocation order; always allocate
> >    *               starting from the last allocated bit. This is less efficient
> >    *               than the default behavior (false).
> > + * @alloc_hint: If true, apply percpu hint for where to start searching for
> > + * 		a free bit.
> >    *
> >    * Return: Zero on success or negative errno on failure.
> >    */
> >   int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
> > -		      gfp_t flags, int node, bool round_robin);
> > +		      gfp_t flags, int node, bool round_robin, bool alloc_hint);
> >   /**
> >    * sbitmap_free() - Free memory used by a &struct sbitmap.
> > @@ -164,6 +166,7 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
> >    */
> >   static inline void sbitmap_free(struct sbitmap *sb)
> >   {
> > +	free_percpu(sb->alloc_hint);
> >   	kfree(sb->map);
> >   	sb->map = NULL;
> >   }
> > @@ -181,19 +184,17 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth);
> >   /**
> >    * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
> >    * @sb: Bitmap to allocate from.
> > - * @alloc_hint: Hint for where to start searching for a free bit.
> >    *
> >    * This operation provides acquire barrier semantics if it succeeds.
> >    *
> >    * Return: Non-negative allocated bit number if successful, -1 otherwise.
> >    */
> > -int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint);
> > +int sbitmap_get(struct sbitmap *sb);
> >   /**
> >    * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
> >    * limiting the depth used from each word.
> >    * @sb: Bitmap to allocate from.
> > - * @alloc_hint: Hint for where to start searching for a free bit.
> >    * @shallow_depth: The maximum number of bits to allocate from a single word.
> >    *
> >    * This rather specific operation allows for having multiple users with
> > @@ -205,8 +206,7 @@ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint);
> >    *
> >    * Return: Non-negative allocated bit number if successful, -1 otherwise.
> >    */
> > -int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
> > -			unsigned long shallow_depth);
> > +int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth);
> >   /**
> >    * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
> > @@ -320,6 +320,18 @@ static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int b
> >   	set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
> >   }
> > +/*
> > + * Pair of sbitmap_get, and this one applies both cleared bit and
> > + * allocation hint.
> > + */
> > +static inline void sbitmap_put(struct sbitmap *sb, unsigned int bitnr)
> > +{
> > +	sbitmap_deferred_clear_bit(sb, bitnr);
> > +
> > +	if (likely(sb->alloc_hint && !sb->round_robin && bitnr < sb->depth))
> > +                *this_cpu_ptr(sb->alloc_hint) = bitnr;
> > +}
> > +
> >   static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
> >   {
> >   	return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
> > @@ -368,7 +380,6 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
> >   static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
> >   {
> >   	kfree(sbq->ws);
> > -	free_percpu(sbq->alloc_hint);
> >   	sbitmap_free(&sbq->sb);
> >   }
> > diff --git a/lib/sbitmap.c b/lib/sbitmap.c
> > index 4e4423414f4d..16f59e99143e 100644
> > --- a/lib/sbitmap.c
> > +++ b/lib/sbitmap.c
> > @@ -9,52 +9,51 @@
> >   #include <linux/sbitmap.h>
> >   #include <linux/seq_file.h>
> > -static int init_alloc_hint(struct sbitmap_queue *sbq, gfp_t flags)
> > +static int init_alloc_hint(struct sbitmap *sb, gfp_t flags)
> >   {
> > -	unsigned depth = sbq->sb.depth;
> > +	unsigned depth = sb->depth;
> > -	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
> > -	if (!sbq->alloc_hint)
> > +	sb->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
> > +	if (!sb->alloc_hint)
> >   		return -ENOMEM;
> > -	if (depth && !sbq->sb.round_robin) {
> > +	if (depth && !sb->round_robin) {
> >   		int i;
> >   		for_each_possible_cpu(i)
> > -			*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
> > +			*per_cpu_ptr(sb->alloc_hint, i) = prandom_u32() % depth;
> >   	}
> > -
> >   	return 0;
> >   }
> > -static inline unsigned update_alloc_hint_before_get(struct sbitmap_queue *sbq,
> > +static inline unsigned update_alloc_hint_before_get(struct sbitmap *sb,
> >   						    unsigned int depth)
> >   {
> >   	unsigned hint;
> > -	hint = this_cpu_read(*sbq->alloc_hint);
> > +	hint = this_cpu_read(*sb->alloc_hint);
> >   	if (unlikely(hint >= depth)) {
> >   		hint = depth ? prandom_u32() % depth : 0;
> > -		this_cpu_write(*sbq->alloc_hint, hint);
> > +		this_cpu_write(*sb->alloc_hint, hint);
> >   	}
> >   	return hint;
> >   }
> > -static inline void update_alloc_hint_after_get(struct sbitmap_queue *sbq,
> > +static inline void update_alloc_hint_after_get(struct sbitmap *sb,
> >   					       unsigned int depth,
> >   					       unsigned int hint,
> >   					       unsigned int nr)
> >   {
> >   	if (nr == -1) {
> >   		/* If the map is full, a hint won't do us much good. */
> > -		this_cpu_write(*sbq->alloc_hint, 0);
> > -	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
> > +		this_cpu_write(*sb->alloc_hint, 0);
> > +	} else if (nr == hint || unlikely(sb->round_robin)) {
> >   		/* Only update the hint if we used it. */
> >   		hint = nr + 1;
> >   		if (hint >= depth - 1)
> >   			hint = 0;
> > -		this_cpu_write(*sbq->alloc_hint, hint);
> > +		this_cpu_write(*sb->alloc_hint, hint);
> >   	}
> >   }
> > @@ -91,7 +90,8 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
> >   }
> >   int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
> > -		      gfp_t flags, int node, bool round_robin)
> > +		      gfp_t flags, int node, bool round_robin,
> > +		      bool alloc_hint)
> >   {
> >   	unsigned int bits_per_word;
> >   	unsigned int i;
> > @@ -123,9 +123,18 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
> >   		return 0;
> >   	}
> > +	if (alloc_hint) {
> > +		if (init_alloc_hint(sb, flags))
> > +			return -ENOMEM;
> > +	} else {
> > +		sb->alloc_hint = NULL;
> > +	}
> > +
> >   	sb->map = kcalloc_node(sb->map_nr, sizeof(*sb->map), flags, node);
> > -	if (!sb->map)
> > +	if (!sb->map) {
> > +		free_percpu(sb->alloc_hint);
> >   		return -ENOMEM;
> > +	}
> >   	for (i = 0; i < sb->map_nr; i++) {
> >   		sb->map[i].depth = min(depth, bits_per_word);
> > @@ -204,7 +213,7 @@ static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
> >   	return nr;
> >   }
> > -int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
> > +static int __sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
> >   {
> >   	unsigned int i, index;
> >   	int nr = -1;
> > @@ -236,10 +245,29 @@ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
> >   	return nr;
> >   }
> > +
> > +int sbitmap_get(struct sbitmap *sb)
> > +{
> > +	int nr;
> > +
> > +	if (likely(sb->alloc_hint)) {
> > +		unsigned int hint, depth;
> > +
> > +		depth = READ_ONCE(sb->depth);
> > +		hint = update_alloc_hint_before_get(sb, depth);
> > +		nr = __sbitmap_get(sb, hint);
> > +		update_alloc_hint_after_get(sb, depth, hint, nr);
> > +	} else {
> > +		nr = __sbitmap_get(sb, 0);
> > +	}
> > +
> > +	return nr;
> > +}
> >   EXPORT_SYMBOL_GPL(sbitmap_get);
> Can't you move the 'alloc_hint' test into update_alloc_hint_before_get()?
> That way we can simplify the code and would avoid the 'if' clause here.

The check is actually not needed. Now only sbitmap_queue calls sbitmap_get &
sbitmap_get_shallow, and sbitmap_queue always applies alloc hint. And
the other two plain sbitmap users(kyber khd->kcq_map[] and hctx->ctx_map) doesn't
use alloc hint and does not call into sbitmap_get & sbitmap_get_shallow
& their put counter-pair.

That said users of sbitmap_get/sbitmap_get_shallow will always allocate alloc hint,
include the introduced user for replacing sdev->device_busy.


Thanks,
Ming

Re: [PATCH V3 for 5.11 11/12] scsi: make sure sdev->queue_depth is <= shost->can_queue

[Ming Lei]

On Wed, Sep 23, 2020 at 08:38:44AM +0100, John Garry wrote:
> On 23/09/2020 02:33, Ming Lei wrote:
> > Obviously scsi device's queue depth can't be > host's can_queue,
> > so make it explicitely in scsi_change_queue_depth().
> 
> ha, why not can_queue * nr_hw_queues?

Yeah, you are right, it should be can_queue * nr_hw_queues for
non-shared-tags.


Thanks,
Ming