On x86, rep stos will be emitted to clear the the blk_mq_alloc_data
struct, as not all members are being initialied. Depending on the
type of CPU, this is a noticeable slowdown compared to just ensuring
that the struct is fully initialized when setup.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
diff --git a/block/blk-mq.c b/block/blk-mq.c
index c2697db59109..9fb43b09a401 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -584,9 +584,13 @@ static struct request *blk_mq_rq_cache_fill(struct request_queue *q,
struct blk_mq_alloc_data data = {
.q = q,
.flags = flags,
+ .shallow_depth = 0,
.cmd_flags = opf,
+ .rq_flags = 0,
.nr_tags = plug->nr_ios,
.cached_rqs = &plug->cached_rqs,
+ .ctx = NULL,
+ .hctx = NULL
};
struct request *rq;
@@ -646,8 +650,13 @@ struct request *blk_mq_alloc_request(struct request_queue *q, blk_opf_t opf,
struct blk_mq_alloc_data data = {
.q = q,
.flags = flags,
+ .shallow_depth = 0,
.cmd_flags = opf,
+ .rq_flags = 0,
.nr_tags = 1,
+ .cached_rqs = NULL,
+ .ctx = NULL,
+ .hctx = NULL
};
int ret;
@@ -675,8 +684,13 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
struct blk_mq_alloc_data data = {
.q = q,
.flags = flags,
+ .shallow_depth = 0,
.cmd_flags = opf,
+ .rq_flags = 0,
.nr_tags = 1,
+ .cached_rqs = NULL,
+ .ctx = NULL,
+ .hctx = NULL
};
u64 alloc_time_ns = 0;
struct request *rq;
@@ -2969,8 +2983,14 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q,
{
struct blk_mq_alloc_data data = {
.q = q,
- .nr_tags = 1,
+ .flags = 0,
+ .shallow_depth = 0,
.cmd_flags = bio->bi_opf,
+ .rq_flags = 0,
+ .nr_tags = 1,
+ .cached_rqs = NULL,
+ .ctx = NULL,
+ .hctx = NULL
};
struct request *rq;
--
Jens Axboe
