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Subject[PATCH 10/13] blk-mq: only allocate a single mq_map per tag_set
Date
The mapping is identical for all queues in a tag_set, so stop wasting
memory for building multiple. Note that for now I've kept the mq_map
pointer in the request_queue, but we'll need to investigate if we can
remove it without suffering from the additional indirection. The same
would apply to the mq_ops pointer as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/blk-mq.c | 22 ++++++++++++++--------
include/linux/blk-mq.h | 1 +
2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f972d32..622cb22 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1930,7 +1930,6 @@ void blk_mq_release(struct request_queue *q)
kfree(hctx);
}

- kfree(q->mq_map);
q->mq_map = NULL;

kfree(q->queue_hw_ctx);
@@ -2029,9 +2028,7 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
if (!q->queue_hw_ctx)
goto err_percpu;

- q->mq_map = blk_mq_make_queue_map(set);
- if (!q->mq_map)
- goto err_map;
+ q->mq_map = set->mq_map;

blk_mq_realloc_hw_ctxs(set, q);
if (!q->nr_hw_queues)
@@ -2081,8 +2078,6 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
return q;

err_hctxs:
- kfree(q->mq_map);
-err_map:
kfree(q->queue_hw_ctx);
err_percpu:
free_percpu(q->queue_ctx);
@@ -2304,14 +2299,22 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
if (!set->tags)
return -ENOMEM;

+ set->mq_map = blk_mq_make_queue_map(set);
+ if (!set->mq_map)
+ goto out_free_tags;
+
if (blk_mq_alloc_rq_maps(set))
- goto enomem;
+ goto out_free_mq_map;

mutex_init(&set->tag_list_lock);
INIT_LIST_HEAD(&set->tag_list);

return 0;
-enomem:
+
+out_free_mq_map:
+ kfree(set->mq_map);
+ set->mq_map = NULL;
+out_free_tags:
kfree(set->tags);
set->tags = NULL;
return -ENOMEM;
@@ -2327,6 +2330,9 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
blk_mq_free_rq_map(set, set->tags[i], i);
}

+ kfree(set->mq_map);
+ set->mq_map = NULL;
+
kfree(set->tags);
set->tags = NULL;
}
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 2498fdf..0a3b138 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -65,6 +65,7 @@ struct blk_mq_hw_ctx {
};

struct blk_mq_tag_set {
+ unsigned int *mq_map;
struct blk_mq_ops *ops;
unsigned int nr_hw_queues;
unsigned int queue_depth; /* max hw supported */
--
2.1.4
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