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: Robert Elliott <elliott@hp.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index f9b85e8..383ea0c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1321,6 +1321,7 @@
continue;
set->ops->exit_request(set->driver_data, tags->rqs[i],
hctx_idx, i);
+ tags->rqs[i] = NULL;
}
}
@@ -1354,8 +1355,9 @@
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;
@@ -1379,8 +1381,9 @@
this_order--;
do {
- page = alloc_pages_node(set->numa_node, GFP_KERNEL,
- this_order);
+ page = alloc_pages_node(set->numa_node,
+ GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY,
+ this_order);
if (page)
break;
if (!this_order--)
@@ -1404,8 +1407,10 @@
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;
@@ -1416,7 +1421,6 @@
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 @@
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 @@
*/
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 @@
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);