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authorJohn Garry <john.garry@huawei.com>2020-08-19 23:20:24 +0800
committerJens Axboe <axboe@kernel.dk>2020-09-03 15:20:47 -0600
commit32bc15afed04bd73e29d713d8db47818d6aa89af (patch)
tree5b7c59ec86d31c5b17a400dd8e5bd26445b7e33b /block/blk-mq-tag.c
parent222a5ae03cdd12e7643f2f64689a39ed547650cb (diff)
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blk-mq: Facilitate a shared sbitmap per tagset
Some SCSI HBAs (such as HPSA, megaraid, mpt3sas, hisi_sas_v3 ..) support multiple reply queues with single hostwide tags. In addition, these drivers want to use interrupt assignment in pci_alloc_irq_vectors(PCI_IRQ_AFFINITY). However, as discussed in [0], CPU hotplug may cause in-flight IO completion to not be serviced when an interrupt is shutdown. That problem is solved in commit bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are offline"). However, to take advantage of that blk-mq feature, the HBA HW queuess are required to be mapped to that of the blk-mq hctx's; to do that, the HBA HW queues need to be exposed to the upper layer. In making that transition, the per-SCSI command request tags are no longer unique per Scsi host - they are just unique per hctx. As such, the HBA LLDD would have to generate this tag internally, which has a certain performance overhead. However another problem is that blk-mq assumes the host may accept (Scsi_host.can_queue * #hw queue) commands. In commit 6eb045e092ef ("scsi: core: avoid host-wide host_busy counter for scsi_mq"), the Scsi host busy counter was removed, which would stop the LLDD being sent more than .can_queue commands; however, it should still be ensured that the block layer does not issue more than .can_queue commands to the Scsi host. To solve this problem, introduce a shared sbitmap per blk_mq_tag_set, which may be requested at init time. New flag BLK_MQ_F_TAG_HCTX_SHARED should be set when requesting the tagset to indicate whether the shared sbitmap should be used. Even when BLK_MQ_F_TAG_HCTX_SHARED is set, a full set of tags and requests are still allocated per hctx; the reason for this is that if tags and requests were only allocated for a single hctx - like hctx0 - it may break block drivers which expect a request be associated with a specific hctx, i.e. not always hctx0. This will introduce extra memory usage. This change is based on work originally from Ming Lei in [1] and from Bart's suggestion in [2]. [0] https://lore.kernel.org/linux-block/alpine.DEB.2.21.1904051331270.1802@nanos.tec.linutronix.de/ [1] https://lore.kernel.org/linux-block/20190531022801.10003-1-ming.lei@redhat.com/ [2] https://lore.kernel.org/linux-block/ff77beff-5fd9-9f05-12b6-826922bace1f@huawei.com/T/#m3db0a602f095cbcbff27e9c884d6b4ae826144be Signed-off-by: John Garry <john.garry@huawei.com> Tested-by: Don Brace<don.brace@microsemi.com> #SCSI resv cmds patches used Tested-by: Douglas Gilbert <dgilbert@interlog.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq-tag.c')
-rw-r--r--block/blk-mq-tag.c51
1 files changed, 47 insertions, 4 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 77fbeae05745..c6d7ebc62bdb 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -197,7 +197,7 @@ static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
* We can hit rq == NULL here, because the tagging functions
* test and set the bit before assigning ->rqs[].
*/
- if (rq && rq->q == hctx->queue)
+ if (rq && rq->q == hctx->queue && rq->mq_hctx == hctx)
return iter_data->fn(hctx, rq, iter_data->data, reserved);
return true;
}
@@ -450,6 +450,38 @@ free_bitmap_tags:
return -ENOMEM;
}
+int blk_mq_init_shared_sbitmap(struct blk_mq_tag_set *set, unsigned int flags)
+{
+ unsigned int depth = set->queue_depth - set->reserved_tags;
+ 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))
+ return -ENOMEM;
+ if (bt_alloc(&set->__breserved_tags, set->reserved_tags,
+ round_robin, node))
+ goto free_bitmap_tags;
+
+ for (i = 0; i < set->nr_hw_queues; i++) {
+ struct blk_mq_tags *tags = set->tags[i];
+
+ tags->bitmap_tags = &set->__bitmap_tags;
+ tags->breserved_tags = &set->__breserved_tags;
+ }
+
+ return 0;
+free_bitmap_tags:
+ sbitmap_queue_free(&set->__bitmap_tags);
+ return -ENOMEM;
+}
+
+void blk_mq_exit_shared_sbitmap(struct blk_mq_tag_set *set)
+{
+ sbitmap_queue_free(&set->__bitmap_tags);
+ sbitmap_queue_free(&set->__breserved_tags);
+}
+
struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
unsigned int reserved_tags,
int node, unsigned int flags)
@@ -469,6 +501,9 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
tags->nr_tags = total_tags;
tags->nr_reserved_tags = reserved_tags;
+ if (flags & BLK_MQ_F_TAG_HCTX_SHARED)
+ return tags;
+
if (blk_mq_init_bitmap_tags(tags, node, alloc_policy) < 0) {
kfree(tags);
return NULL;
@@ -478,8 +513,10 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
void blk_mq_free_tags(struct blk_mq_tags *tags, unsigned int flags)
{
- sbitmap_queue_free(&tags->__bitmap_tags);
- sbitmap_queue_free(&tags->__breserved_tags);
+ if (!(flags & BLK_MQ_F_TAG_HCTX_SHARED)) {
+ sbitmap_queue_free(tags->bitmap_tags);
+ sbitmap_queue_free(tags->breserved_tags);
+ }
kfree(tags);
}
@@ -498,7 +535,8 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
*/
if (tdepth > tags->nr_tags) {
struct blk_mq_tag_set *set = hctx->queue->tag_set;
- unsigned int flags = set->flags;
+ /* Only sched tags can grow, so clear HCTX_SHARED flag */
+ unsigned int flags = set->flags & ~BLK_MQ_F_TAG_HCTX_SHARED;
struct blk_mq_tags *new;
bool ret;
@@ -537,6 +575,11 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
return 0;
}
+void blk_mq_tag_resize_shared_sbitmap(struct blk_mq_tag_set *set, unsigned int size)
+{
+ sbitmap_queue_resize(&set->__bitmap_tags, size - set->reserved_tags);
+}
+
/**
* blk_mq_unique_tag() - return a tag that is unique queue-wide
* @rq: request for which to compute a unique tag