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authorPavel Begunkov <asml.silence@gmail.com>2023-01-17 11:42:15 +0000
committerJens Axboe <axboe@kernel.dk>2023-01-17 09:56:52 -0700
commit7746564793978fe2f43b18a302b22dca0ad3a0e8 (patch)
tree95ce46a90bfbd263b9938dca5aa7b63b094d1641
parent9d6033e350694a67885605674244d43c9559dc36 (diff)
downloadlinux-7746564793978fe2f43b18a302b22dca0ad3a0e8.tar.bz2
block: fix hctx checks for batch allocation
When there are no read queues read requests will be assigned a default queue on allocation. However, blk_mq_get_cached_request() is not prepared for that and will fail all attempts to grab read requests from the cache. Worst case it doubles the number of requests allocated, roughly half of which will be returned by blk_mq_free_plug_rqs(). It only affects batched allocations and so is io_uring specific. For reference, QD8 t/io_uring benchmark improves by 20-35%. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/80d4511011d7d4751b4cf6375c4e38f237d935e3.1673955390.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--block/blk-mq.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2c49b4151da1..9d463f7563bc 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2890,6 +2890,7 @@ static inline struct request *blk_mq_get_cached_request(struct request_queue *q,
struct blk_plug *plug, struct bio **bio, unsigned int nsegs)
{
struct request *rq;
+ enum hctx_type type, hctx_type;
if (!plug)
return NULL;
@@ -2902,7 +2903,10 @@ static inline struct request *blk_mq_get_cached_request(struct request_queue *q,
return NULL;
}
- if (blk_mq_get_hctx_type((*bio)->bi_opf) != rq->mq_hctx->type)
+ type = blk_mq_get_hctx_type((*bio)->bi_opf);
+ hctx_type = rq->mq_hctx->type;
+ if (type != hctx_type &&
+ !(type == HCTX_TYPE_READ && hctx_type == HCTX_TYPE_DEFAULT))
return NULL;
if (op_is_flush(rq->cmd_flags) != op_is_flush((*bio)->bi_opf))
return NULL;