From a516440542afcb9647f88d12c35640baf02d07ea Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 10 Sep 2014 09:02:03 -0600 Subject: [PATCH] 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 Signed-off-by: Jens Axboe --- block/blk-mq.c | 88 +++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 69 insertions(+), 19 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index f9b85e83d9ba..383ea0cb1f0a 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -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; @@ -1379,8 +1381,9 @@ 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, - 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 @@ 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; @@ -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);