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dm: block_if: support bypassing BST_BLOCK logic

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With current implementation, in blockif_dequeue/blockif_complete,
if the current request is consecutive to any request in penq or busyq,
current request's status is set to BST_BLOCK. Then, this request is blocked
until the prior request, which blocks it, is completed.
It indicates that consecutive requests are executed sequentially.

This patch adds a flag `no_bst_block` to bypass such logic because:
1. the benefit of this logic is not noticeable;
2. there is a chance that a request is enqueued in block_if_queue but
   not dequeued when this logic is triggered along with the io_uring mechanism;

Example to use this flag:
`add_virtual_device                     5 virtio-blk /dev/nvme1n1,no_bst_block`

Note:
When io_uring is enabled, the BST_BLOCK logic would be bypassed.

Tracked-On: #8612

Signed-off-by: Shiqing Gao <shiqing.gao@intel.com>
Acked-by: Wang, Yu1 <yu1.wang@intel.com>
This commit is contained in:
Shiqing Gao 2024-01-16 15:03:57 +08:00 committed by acrnsi-robot
parent 11c8907464
commit 80b1edabf5
1 changed files with 50 additions and 26 deletions
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32
devicemodel/hw/block_if.c
View File

@ -164,6 +164,17 @@ struct blockif_ctxt {
/* whether bypass the Service VM's page cache or not */
uint8_t bypass_host_cache;
/*
* whether enable BST_BLOCK logic in blockif_dequeue/blockif_complete or not.
*
* If the BST_BLOCK logic is enabled, following check would be done:
* if the current request is consecutive to any request in penq or busyq,
* current request's status is set to BST_BLOCK. Then, this request is blocked until the prior request,
* which blocks it, is completed.
* It indicates that consecutive requests are executed sequentially.
*/
uint8_t bst_block;
};
static pthread_once_t blockif_once = PTHREAD_ONCE_INIT;
@ -212,6 +223,9 @@ blockif_enqueue(struct blockif_queue *bq, struct blockif_req *breq,
TAILQ_REMOVE(&bq->freeq, be, link);
be->req = breq;
be->op = op;
be->status = BST_PEND;
if (bq->bc->bst_block == 1) {
switch (op) {
case BOP_READ:
case BOP_WRITE:
@ -235,10 +249,10 @@ blockif_enqueue(struct blockif_queue *bq, struct blockif_req *breq,
break;
}
}
if (tbe == NULL)
be->status = BST_PEND;
else
if (tbe != NULL)
be->status = BST_BLOCK;
}
TAILQ_INSERT_TAIL(&bq->pendq, be, link);
return (be->status == BST_PEND);
}
@ -271,10 +285,13 @@ blockif_complete(struct blockif_queue *bq, struct blockif_elem *be)
TAILQ_REMOVE(&bq->busyq, be, link);
else
TAILQ_REMOVE(&bq->pendq, be, link);
if (bq->bc->bst_block == 1) {
TAILQ_FOREACH(tbe, &bq->pendq, link) {
if (tbe->req->offset == be->block)
tbe->status = BST_PEND;
}
}
be->tid = 0;
be->status = BST_FREE;
be->req = NULL;
@ -1293,7 +1310,7 @@ blockif_open(const char *optstr, const char *ident, int queue_num, struct iothre
int max_discard_sectors, max_discard_seg, discard_sector_alignment;
off_t probe_arg[] = {0, 0};
int aio_mode;
int bypass_host_cache, open_flag;
int bypass_host_cache, open_flag, bst_block;
pthread_once(&blockif_once, blockif_init);
@ -1318,6 +1335,9 @@ blockif_open(const char *optstr, const char *ident, int queue_num, struct iothre
/* By default, do NOT bypass Service VM's page cache. */
bypass_host_cache = 0;
/* By default, bst_block is 1, meaning that the BST_BLOCK logic in blockif_dequeue is enabled. */
bst_block = 1;
candiscard = 0;
if (queue_num <= 0)
@ -1344,6 +1364,8 @@ blockif_open(const char *optstr, const char *ident, int queue_num, struct iothre
ro = 1;
else if (!strcmp(cp, "nocache"))
bypass_host_cache = 1;
else if (!strcmp(cp, "no_bst_block"))
bst_block = 0;
else if (!strncmp(cp, "discard", strlen("discard"))) {
strsep(&cp, "=");
if (cp != NULL) {
@ -1558,8 +1580,10 @@ blockif_open(const char *optstr, const char *ident, int queue_num, struct iothre
if (bc->aio_mode == AIO_MODE_IO_URING) {
bc->ops = &blockif_ops_iou;
bc->bst_block = 0;
} else {
bc->ops = &blockif_ops_thread_pool;
bc->bst_block = bst_block;
}
bc->bq_num = queue_num;