If the underlying queue returns BLK_STS_RESOURCE, we let dm-rq
handle the requeue instead of blk-mq, then I/O merge can be
improved because underlying's out-of-resource can be perceived
and handled by dm-rq now.
Follows IOPS test of mpath on lpfc, fio(libaio, bs:4k, dio,
queue_depth:64, 8 jobs).
1) blk-mq none scheduler
-----------------------------------------------------
IOPS(K) |v4.14-rc2 |v4.14-rc2 with| v4.14-rc2 with
| |[1][2] | [1] [2] [3]
-----------------------------------------------------
read | 53.69 | 40.26 | 94.61
-----------------------------------------------------
randread | 24.64 | 30.08 | 35.57
-----------------------------------------------------
write | 39.55 | 41.51 | 216.84
-----------------------------------------------------
randwrite | 33.97 | 34.27 | 33.98
-----------------------------------------------------
2) blk-mq mq-deadline scheduler
-----------------------------------------------------
IOPS(K) |v4.14-rc2 |v4.14-rc2 with| v4.14-rc2 with
| |[1][2] | [1] [2] [3]
-----------------------------------------------------
IOPS(K) |MQ-DEADLINE |MQ-DEADLINE |MQ-DEADLINE
-----------------------------------------------------
read | 23.81 | 21.91 | 89.94
-----------------------------------------------------
randread | 38.47 | 38.96 | 38.02
-----------------------------------------------------
write | 39.52 | 40.2 | 225.75
-----------------------------------------------------
randwrite | 34.8 | 33.73 | 33.44
-----------------------------------------------------
[1] [PATCH V5 0/7] blk-mq-sched: improve sequential I/O performance(part 1)
https://marc.info/?l=linux-block&m=150676854821077&w=2
[2] [PATCH V5 0/8] blk-mq: improve bio merge for none scheduler
https://marc.info/?l=linux-block&m=150677085521416&w=2
[3] this patchset
Signed-off-by: Ming Lei <ming....@redhat.com>
---
block/blk-mq.c | 17 +----------------
drivers/md/dm-rq.c | 14 ++++++++++++--
2 files changed, 13 insertions(+), 18 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9a3a561a63b5..58d2268f9733 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1467,17 +1467,6 @@ void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx,
struct request *rq,
blk_mq_hctx_mark_pending(hctx, ctx);
}
-static void blk_mq_request_direct_insert(struct blk_mq_hw_ctx *hctx,
- struct request *rq)
-{
- spin_lock(&hctx->lock);
- list_add_tail(&rq->queuelist, &hctx->dispatch);
- set_bit(BLK_MQ_S_DISPATCH_BUSY, &hctx->state);
- spin_unlock(&hctx->lock);
-
- blk_mq_run_hw_queue(hctx, false);
-}
-
/*
* Should only be used carefully, when the caller knows we want to
* bypass a potential IO scheduler on the target device.
@@ -1487,12 +1476,8 @@ blk_status_t blk_mq_request_bypass_insert(struct request
*rq)
struct blk_mq_ctx *ctx = rq->mq_ctx;
struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(rq->q, ctx->cpu);
blk_qc_t cookie;
- blk_status_t ret;
- ret = blk_mq_try_issue_directly(hctx, rq, &cookie, true);
- if (ret == BLK_STS_RESOURCE)
- blk_mq_request_direct_insert(hctx, rq);
- return ret;
+ return blk_mq_try_issue_directly(hctx, rq, &cookie, true);
}
void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 2ef524bddd38..feb49c4d6fa2 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -405,7 +405,7 @@ static void end_clone_request(struct request *clone,
blk_status_t error)
dm_complete_request(tio->orig, error);
}
-static void dm_dispatch_clone_request(struct request *clone, struct request
*rq)
+static blk_status_t dm_dispatch_clone_request(struct request *clone, struct
request *rq)
{
blk_status_t r;
@@ -417,6 +417,7 @@ static void dm_dispatch_clone_request(struct request
*clone, struct request *rq)
if (r != BLK_STS_OK && r != BLK_STS_RESOURCE)
/* must complete clone in terms of original request */
dm_complete_request(rq, r);
+ return r;
}
static int dm_rq_bio_constructor(struct bio *bio, struct bio *bio_orig,
@@ -490,8 +491,10 @@ static int map_request(struct dm_rq_target_io *tio)
struct request *rq = tio->orig;
struct request *cache = tio->clone;
struct request *clone = cache;
+ blk_status_t ret;
r = ti->type->clone_and_map_rq(ti, rq, &tio->info, &clone);
+ again:
switch (r) {
case DM_MAPIO_SUBMITTED:
/* The target has taken the I/O to submit by itself later */
@@ -509,7 +512,14 @@ static int map_request(struct dm_rq_target_io *tio)
/* The target has remapped the I/O so dispatch it */
trace_block_rq_remap(clone->q, clone, disk_devt(dm_disk(md)),
blk_rq_pos(rq));
- dm_dispatch_clone_request(clone, rq);
+ ret = dm_dispatch_clone_request(clone, rq);
+ if (ret == BLK_STS_RESOURCE) {
+ if (!rq->q->mq_ops)
+ r = DM_MAPIO_DELAY_REQUEUE;
+ else
+ r = DM_MAPIO_REQUEUE;
+ goto again;
+ }
break;
case DM_MAPIO_REQUEUE:
/* The target wants to requeue the I/O */
--
2.9.5
