This is the blk-mq part to support tag allocation policy. The default
allocation policy isn't changed (though it's not a strict FIFO). The new
policy is round-robin for libata. But it's a try-best implementation. If
multiple tasks are competing, the tags returned will be mixed (which is
unavoidable even with !mq, as requests from different tasks can be
mixed in queue)
Cc: Jens Axboe <axboe@xxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
---
block/blk-mq-tag.c | 39 ++++++++++++++++++++++++---------------
block/blk-mq-tag.h | 4 +++-
block/blk-mq.c | 3 ++-
drivers/scsi/scsi_lib.c | 2 ++
include/linux/blk-mq.h | 8 ++++++++
5 files changed, 39 insertions(+), 17 deletions(-)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 60c9d4a..231e1bc 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -140,10 +140,11 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
return atomic_read(&hctx->nr_active) < depth;
}
-static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
+static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag,
+ bool nowrap)
{
int tag, org_last_tag, end;
- bool wrap = last_tag != 0;
+ bool wrap = last_tag != 0 && !nowrap;
org_last_tag = last_tag;
end = bm->depth;
@@ -169,6 +170,8 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
return tag;
}
+#define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR)
+
/*
* Straight forward bitmap tag implementation, where each bit is a tag
* (cleared == free, and set == busy). The small twist is using per-cpu
@@ -181,7 +184,7 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
* until the map is exhausted.
*/
static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
- unsigned int *tag_cache)
+ unsigned int *tag_cache, struct blk_mq_tags *tags)
{
unsigned int last_tag, org_last_tag;
int index, i, tag;
@@ -193,7 +196,8 @@ static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
index = TAG_TO_INDEX(bt, last_tag);
for (i = 0; i < bt->map_nr; i++) {
- tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag));
+ tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag),
+ BT_ALLOC_RR(tags));
if (tag != -1) {
tag += (index << bt->bits_per_word);
goto done;
@@ -212,7 +216,7 @@ static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
* up using the specific cached tag.
*/
done:
- if (tag == org_last_tag) {
+ if (tag == org_last_tag || unlikely(BT_ALLOC_RR(tags))) {
last_tag = tag + 1;
if (last_tag >= bt->depth - 1)
last_tag = 0;
@@ -241,13 +245,13 @@ static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
static int bt_get(struct blk_mq_alloc_data *data,
struct blk_mq_bitmap_tags *bt,
struct blk_mq_hw_ctx *hctx,
- unsigned int *last_tag)
+ unsigned int *last_tag, struct blk_mq_tags *tags)
{
struct bt_wait_state *bs;
DEFINE_WAIT(wait);
int tag;
- tag = __bt_get(hctx, bt, last_tag);
+ tag = __bt_get(hctx, bt, last_tag, tags);
if (tag != -1)
return tag;
@@ -258,7 +262,7 @@ static int bt_get(struct blk_mq_alloc_data *data,
do {
prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);
- tag = __bt_get(hctx, bt, last_tag);
+ tag = __bt_get(hctx, bt, last_tag, tags);
if (tag != -1)
break;
@@ -273,7 +277,7 @@ static int bt_get(struct blk_mq_alloc_data *data,
* Retry tag allocation after running the hardware queue,
* as running the queue may also have found completions.
*/
- tag = __bt_get(hctx, bt, last_tag);
+ tag = __bt_get(hctx, bt, last_tag, tags);
if (tag != -1)
break;
@@ -304,7 +308,7 @@ static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
int tag;
tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,
- &data->ctx->last_tag);
+ &data->ctx->last_tag, data->hctx->tags);
if (tag >= 0)
return tag + data->hctx->tags->nr_reserved_tags;
@@ -320,7 +324,8 @@ static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
return BLK_MQ_TAG_FAIL;
}
- tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero);
+ tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero,
+ data->hctx->tags);
if (tag < 0)
return BLK_MQ_TAG_FAIL;
@@ -392,7 +397,8 @@ void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
BUG_ON(real_tag >= tags->nr_tags);
bt_clear_tag(&tags->bitmap_tags, real_tag);
- *last_tag = real_tag;
+ if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO))
+ *last_tag = real_tag;
} else {
BUG_ON(tag >= tags->nr_reserved_tags);
bt_clear_tag(&tags->breserved_tags, tag);
@@ -529,10 +535,12 @@ static void bt_free(struct blk_mq_bitmap_tags *bt)
}
static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
- int node)
+ int node, int alloc_policy)
{
unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
+ tags->alloc_policy = alloc_policy;
+
if (bt_alloc(&tags->bitmap_tags, depth, node, false))
goto enomem;
if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true))
@@ -546,7 +554,8 @@ static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
}
struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
- unsigned int reserved_tags, int node)
+ unsigned int reserved_tags,
+ int node, int alloc_policy)
{
struct blk_mq_tags *tags;
@@ -562,7 +571,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
tags->nr_tags = total_tags;
tags->nr_reserved_tags = reserved_tags;
- return blk_mq_init_bitmap_tags(tags, node);
+ return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
}
void blk_mq_free_tags(struct blk_mq_tags *tags)
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index a6fa0fc..90767b3 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -42,10 +42,12 @@ struct blk_mq_tags {
struct request **rqs;
struct list_head page_list;
+
+ int alloc_policy;
};
-extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node);
+extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node, int alloc_policy);
extern void blk_mq_free_tags(struct blk_mq_tags *tags);
extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2f95747..fffbb83 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1423,7 +1423,8 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
size_t rq_size, left;
tags = blk_mq_init_tags(set->queue_depth, set->reserved_tags,
- set->numa_node);
+ set->numa_node,
+ BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
if (!tags)
return NULL;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9ea95dd..49ab115 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2188,6 +2188,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
shost->tag_set.cmd_size = cmd_size;
shost->tag_set.numa_node = NUMA_NO_NODE;
shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;
+ shost->tag_set.flags |=
+ BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
shost->tag_set.driver_data = shost;
return blk_mq_alloc_tag_set(&shost->tag_set);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 5735e71..623d61d 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -146,6 +146,8 @@ enum {
BLK_MQ_F_SG_MERGE = 1 << 2,
BLK_MQ_F_SYSFS_UP = 1 << 3,
BLK_MQ_F_DEFER_ISSUE = 1 << 4,
+ BLK_MQ_F_ALLOC_POLICY_START_BIT = 8,
+ BLK_MQ_F_ALLOC_POLICY_BITS = 1,
BLK_MQ_S_STOPPED = 0,
BLK_MQ_S_TAG_ACTIVE = 1,
@@ -154,6 +156,12 @@ enum {
BLK_MQ_CPU_WORK_BATCH = 8,
};
+#define BLK_MQ_FLAG_TO_ALLOC_POLICY(flags) \
+ ((flags >> BLK_MQ_F_ALLOC_POLICY_START_BIT) & \
+ ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1))
+#define BLK_ALLOC_POLICY_TO_MQ_FLAG(policy) \
+ ((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
+ << BLK_MQ_F_ALLOC_POLICY_START_BIT)
struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);
void blk_mq_finish_init(struct request_queue *q);
--
1.8.1
--
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