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| author | Bart Van Assche <bvanassche@acm.org> | 2021-08-05 10:41:59 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2021-08-05 11:49:21 -0600 |
| commit | 90b7198001f23ea37d3b46dc631bdaa2357a20b1 (patch) | |
| tree | 6f2e6f129a9444b686340c7d8ea9b3b8f4189016 /block/elevator.c | |
| parent | 2bc1f6e442eec88fa60f1ee6bef2c9871227cf8a (diff) | |
| download | lwn-90b7198001f23ea37d3b46dc631bdaa2357a20b1.tar.gz lwn-90b7198001f23ea37d3b46dc631bdaa2357a20b1.zip | |
blk-mq: Introduce the BLK_MQ_F_NO_SCHED_BY_DEFAULT flag
elevator_get_default() uses the following algorithm to select an I/O
scheduler from inside add_disk():
- In case of a single hardware queue or if sharing hardware queues across
multiple request queues (BLK_MQ_F_TAG_HCTX_SHARED), use mq-deadline.
- Otherwise, use 'none'.
This is a good choice for most but not for all block drivers. Make it
possible to override the selection of mq-deadline with a new flag,
namely BLK_MQ_F_NO_SCHED_BY_DEFAULT.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Martijn Coenen <maco@android.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210805174200.3250718-2-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/elevator.c')
| -rw-r--r-- | block/elevator.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/block/elevator.c b/block/elevator.c index 52ada14cfe45..d0295e68f481 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -630,6 +630,9 @@ static inline bool elv_support_iosched(struct request_queue *q) */ static struct elevator_type *elevator_get_default(struct request_queue *q) { + if (q->tag_set && q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT) + return NULL; + if (q->nr_hw_queues != 1 && !blk_mq_is_sbitmap_shared(q->tag_set->flags)) return NULL; |