Re: [PATCH v2] blk-mq: Use request queue-wide tags for tagset-wide sbitmap

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+static int blk_mq_init_sched_shared_sbitmap(struct request_queue *queue)
+{
+	struct blk_mq_tag_set *set = queue->tag_set;
+	int ret;
+
+	/*
+	 * Set initial depth at max so that we don't need to reallocate for
+	 * updating nr_requests.
+	 */
+	ret = blk_mq_init_bitmaps(&queue->sched_bitmap_tags,
+				  &queue->sched_breserved_tags,
+				  set, MAX_SCHED_RQ, set->reserved_tags);
+	if (ret)
+		return ret;
+
+	sbitmap_queue_resize(&queue->sched_bitmap_tags,
+			     queue->nr_requests - set->reserved_tags);
+
+	return 0;
+}
+
+static void blk_mq_exit_sched_shared_sbitmap(struct request_queue *queue)
+{
+	sbitmap_queue_free(&queue->sched_bitmap_tags);
+	sbitmap_queue_free(&queue->sched_breserved_tags);
+}
+
  int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
  {
  	struct blk_mq_hw_ctx *hctx;
@@ -578,12 +598,25 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
  	queue_for_each_hw_ctx(q, hctx, i) {
  		ret = blk_mq_sched_alloc_tags(q, hctx, i);
  		if (ret)
-			goto err;
+			goto err_free_tags;
+	}
+
+	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
+		ret = blk_mq_init_sched_shared_sbitmap(q);
+		if (ret)
+			goto err_free_tags;
+
+		queue_for_each_hw_ctx(q, hctx, i) {
+			hctx->sched_tags->bitmap_tags =
+						&q->sched_bitmap_tags;
+			hctx->sched_tags->breserved_tags =
+						&q->sched_breserved_tags;
+		}
The above assignment can be folded into blk_mq_init_sched_shared_sbitmap().


ok

  	}
ret = e->ops.init_sched(q, e);
  	if (ret)
-		goto err;
+		goto err_free_sbitmap;
blk_mq_debugfs_register_sched(q); @@ -603,7 +636,10 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e) return 0; -err:
+err_free_sbitmap:
+	if (blk_mq_is_sbitmap_shared(q->tag_set->flags))
+		blk_mq_exit_sched_shared_sbitmap(q);
+err_free_tags:
  	blk_mq_sched_free_requests(q);
  	blk_mq_sched_tags_teardown(q);
  	q->elevator = NULL;
@@ -641,5 +677,7 @@ void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
  	if (e->type->ops.exit_sched)
  		e->type->ops.exit_sched(e);
  	blk_mq_sched_tags_teardown(q);
+	if (blk_mq_is_sbitmap_shared(q->tag_set->flags))
+		blk_mq_exit_sched_shared_sbitmap(q);
The above two lines can be moved to blk_mq_sched_tags_teardown().

blk_mq_sched_tags_teardown() is also used in blk_mq_init_sched() to undo the blk_mq_sched_alloc_tags() calls; however, in that same function we call blk_mq_sched_alloc_tags() and blk_mq_init_sched_shared_sbitmap() separately, so can't combine into a single teardown function.


  	q->elevator = NULL;
  }
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 5b18ab915c65..aff037cfd8e7 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -5,6 +5,8 @@
  #include "blk-mq.h"
  #include "blk-mq-tag.h"
+#define MAX_SCHED_RQ (16 * BLKDEV_MAX_RQ)
+
  void blk_mq_sched_assign_ioc(struct request *rq);
bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 2a37731e8244..e3ab8631be22 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -13,6 +13,7 @@
  #include <linux/delay.h>
  #include "blk.h"
  #include "blk-mq.h"
+#include "blk-mq-sched.h"
  #include "blk-mq-tag.h"
/*
@@ -466,19 +467,39 @@ static int blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
  	return -ENOMEM;
  }
-int blk_mq_init_shared_sbitmap(struct blk_mq_tag_set *set, unsigned int flags)
+int blk_mq_init_bitmaps(struct sbitmap_queue *bitmap_tags,
+			struct sbitmap_queue *breserved_tags,
+			struct blk_mq_tag_set *set,
The 'set' parameter can be killed, meantime pass 'node' & 'alloc_policy',
just like blk_mq_init_bitmap_tags()'s type, then blk_mq_init_bitmaps()
can be re-used by blk_mq_init_bitmap_tags() for avoiding to duplicate
bitmap allocation code.

I was thinking that we could consolidate here, so let me check this.


+			unsigned int queue_depth, unsigned int reserved)
  {
-	unsigned int depth = set->queue_depth - set->reserved_tags;
+	unsigned int depth = queue_depth - reserved;
  	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags);
  	bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
-	int i, node = set->numa_node;
- if (bt_alloc(&set->__bitmap_tags, depth, round_robin, node))
+	if (bt_alloc(bitmap_tags, depth, round_robin, set->numa_node))
  		return -ENOMEM;
-	if (bt_alloc(&set->__breserved_tags, set->reserved_tags,
-		     round_robin, node))
+	if (bt_alloc(breserved_tags, set->reserved_tags,
s/set->reserved_tags/reserved/

ok

Thanks!




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