diff options
| author | Song Liu <songliubraving@fb.com> | 2021-09-07 16:03:38 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2021-09-07 17:05:12 -0600 |
| commit | 7f2a6a69f7ced6db8220298e0497cf60482a9d4b (patch) | |
| tree | a0cd135c8be2a9327e124f5788057ff9d83b547a /block | |
| parent | 0dca4462ed0681649fdcd5700a6ddfbaa65fa178 (diff) | |
| download | lwn-7f2a6a69f7ced6db8220298e0497cf60482a9d4b.tar.gz lwn-7f2a6a69f7ced6db8220298e0497cf60482a9d4b.zip | |
blk-mq: allow 4x BLK_MAX_REQUEST_COUNT at blk_plug for multiple_queues
Limiting number of request to BLK_MAX_REQUEST_COUNT at blk_plug hurts
performance for large md arrays. [1] shows resync speed of md array drops
for md array with more than 16 HDDs.
Fix this by allowing more request at plug queue. The multiple_queue flag
is used to only apply higher limit to multiple queue cases.
[1] https://lore.kernel.org/linux-raid/CAFDAVznS71BXW8Jxv6k9dXc2iR3ysX3iZRBww_rzA8WifBFxGg@mail.gmail.com/
Tested-by: Marcin Wanat <marcin.wanat@gmail.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-mq.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 944049982e6e..6b5a509fbaff 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2135,6 +2135,18 @@ static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq) } } +/* + * Allow 4x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple + * queues. This is important for md arrays to benefit from merging + * requests. + */ +static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug) +{ + if (plug->multiple_queues) + return BLK_MAX_REQUEST_COUNT * 4; + return BLK_MAX_REQUEST_COUNT; +} + /** * blk_mq_submit_bio - Create and send a request to block device. * @bio: Bio pointer. @@ -2231,7 +2243,7 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio) else last = list_entry_rq(plug->mq_list.prev); - if (request_count >= BLK_MAX_REQUEST_COUNT || (last && + if (request_count >= blk_plug_max_rq_count(plug) || (last && blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) { blk_flush_plug_list(plug, false); trace_block_plug(q); |