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Commit a5164405 authored by Jens Axboe's avatar Jens Axboe
Browse files

blk-mq: scale depth and rq map appropriate if low on memory 



If we are running in a kdump environment, resources are scarce.
For some SCSI setups with a huge set of shared tags, we run out
of memory allocating what the drivers is asking for. So implement
a scale back logic to reduce the tag depth for those cases, allowing
the driver to successfully load.

We should extend this to detect low memory situations, and implement
a sane fallback for those (1 queue, 64 tags, or something like that).

Tested-by: default avatarRobert Elliott <elliott@hp.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent df35c7c9

block/blk-mq.c

+69 −19
Original line number Diff line number Diff line
@@ -1321,6 +1321,7 @@ static void blk_mq_free_rq_map(struct blk_mq_tag_set *set, 
				continue;

			set->ops->exit_request(set->driver_data, tags->rqs[i],

						hctx_idx, i);

			tags->rqs[i] = NULL;

		}

	}
@@ -1354,8 +1355,9 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set, 


	INIT_LIST_HEAD(&tags->page_list);



	tags->rqs = kmalloc_node(set->queue_depth * sizeof(struct request *),

					GFP_KERNEL, set->numa_node);

	tags->rqs = kzalloc_node(set->queue_depth * sizeof(struct request *),

				 GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY,

				 set->numa_node);

	if (!tags->rqs) {

		blk_mq_free_tags(tags);

		return NULL;
@@ -1379,7 +1381,8 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set, 
			this_order--;



		do {

			page = alloc_pages_node(set->numa_node, GFP_KERNEL,

			page = alloc_pages_node(set->numa_node,

				GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY,

				this_order);

			if (page)

				break;
@@ -1404,9 +1407,11 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set, 
			if (set->ops->init_request) {

				if (set->ops->init_request(set->driver_data,

						tags->rqs[i], hctx_idx, i,

						set->numa_node))

						set->numa_node)) {

					tags->rqs[i] = NULL;

					goto fail;

				}

			}



			p += rq_size;

			i++;
@@ -1416,7 +1421,6 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set, 
	return tags;



fail:

	pr_warn("%s: failed to allocate requests\n", __func__);

	blk_mq_free_rq_map(set, tags, hctx_idx);

	return NULL;

}
@@ -1936,6 +1940,61 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb, 
	return NOTIFY_OK;

}



static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)

{

	int i;



	for (i = 0; i < set->nr_hw_queues; i++) {

		set->tags[i] = blk_mq_init_rq_map(set, i);

		if (!set->tags[i])

			goto out_unwind;

	}



	return 0;



out_unwind:

	while (--i >= 0)

		blk_mq_free_rq_map(set, set->tags[i], i);



	set->tags = NULL;

	return -ENOMEM;

}



/*

 * Allocate the request maps associated with this tag_set. Note that this

 * may reduce the depth asked for, if memory is tight. set->queue_depth

 * will be updated to reflect the allocated depth.

 */

static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)

{

	unsigned int depth;

	int err;



	depth = set->queue_depth;

	do {

		err = __blk_mq_alloc_rq_maps(set);

		if (!err)

			break;



		set->queue_depth >>= 1;

		if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {

			err = -ENOMEM;

			break;

		}

	} while (set->queue_depth);



	if (!set->queue_depth || err) {

		pr_err("blk-mq: failed to allocate request map\n");

		return -ENOMEM;

	}



	if (depth != set->queue_depth)

		pr_info("blk-mq: reduced tag depth (%u -> %u)\n",

						depth, set->queue_depth);



	return 0;

}



/*

 * Alloc a tag set to be associated with one or more request queues.

 * May fail with EINVAL for various error conditions. May adjust the
@@ -1944,8 +2003,6 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb, 
 */

int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)

{

	int i;



	if (!set->nr_hw_queues)

		return -EINVAL;

	if (!set->queue_depth)
@@ -1966,25 +2023,18 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set) 
				 sizeof(struct blk_mq_tags *),

				 GFP_KERNEL, set->numa_node);

	if (!set->tags)

		goto out;

		return -ENOMEM;



	for (i = 0; i < set->nr_hw_queues; i++) {

		set->tags[i] = blk_mq_init_rq_map(set, i);

		if (!set->tags[i])

			goto out_unwind;

	}

	if (blk_mq_alloc_rq_maps(set))

		goto enomem;



	mutex_init(&set->tag_list_lock);

	INIT_LIST_HEAD(&set->tag_list);



	return 0;



out_unwind:

	while (--i >= 0)

		blk_mq_free_rq_map(set, set->tags[i], i);

enomem:

	kfree(set->tags);

	set->tags = NULL;

out:

	return -ENOMEM;

}

EXPORT_SYMBOL(blk_mq_alloc_tag_set);