diff options
authorMing Lei <>2021-04-06 11:19:33 +0800
committerJens Axboe <>2021-04-07 10:15:23 -0600
commit580dca8143d215977811bd2ff881e1e4f6ff39f0 (patch)
parent393bb12e00580aaa23356504eed38d8f5571153a (diff)
blk-mq: set default elevator as deadline in case of hctx shared tagset
Yanhui found that write performance is degraded a lot after applying hctx shared tagset on one test machine with megaraid_sas. And turns out it is caused by none scheduler which becomes default elevator caused by hctx shared tagset patchset. Given more scsi HBAs will apply hctx shared tagset, and the similar performance exists for them too. So keep previous behavior by still using default mq-deadline for queues which apply hctx shared tagset, just like before. Fixes: 32bc15afed04 ("blk-mq: Facilitate a shared sbitmap per tagset") Reported-by: Yanhui Ma <> Cc: John Garry <> Cc: Hannes Reinecke <> Signed-off-by: Ming Lei <> Reviewed-by: Martin K. Petersen <> Reviewed-by: Bart Van Assche <> Reviewed-by: John Garry <> Link: Signed-off-by: Jens Axboe <>
1 files changed, 2 insertions, 1 deletions
diff --git a/block/elevator.c b/block/elevator.c
index 293c5c81397a..440699c28119 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -621,7 +621,8 @@ static inline bool elv_support_iosched(struct request_queue *q)
static struct elevator_type *elevator_get_default(struct request_queue *q)
- if (q->nr_hw_queues != 1)
+ if (q->nr_hw_queues != 1 &&
+ !blk_mq_is_sbitmap_shared(q->tag_set->flags))
return NULL;
return elevator_get(q, "mq-deadline", false);