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| author | Bart Van Assche <bvanassche@acm.org> | 2021-06-18 03:44:52 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2021-06-22 00:03:40 +0300 |
| commit | d672d325b1492f5b0e54b7226f01e2d57b58bfb4 (patch) | |
| tree | a9a5dea29e7aac94a5dfd5d3b2f3b36457c04eab /block/mq-deadline.c | |
| parent | 07757588e5076748308dd95ee2e3cd0b82ebb8c4 (diff) | |
| download | linux-d672d325b1492f5b0e54b7226f01e2d57b58bfb4.tar.xz | |
block/mq-deadline: Micro-optimize the batching algorithm
When dispatching the first request of a batch, the deadline_move_request()
call clears .next_rq[] for the opposite data direction. .next_rq[] is not
restored when changing data direction. Fix this by not clearing .next_rq[]
and by keeping track of the data direction of a batch in a variable instead.
This patch is a micro-optimization because:
- The number of deadline_next_request() calls for the read direction is
halved.
- The number of times that deadline_next_request() returns NULL is reduced.
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210618004456.7280-13-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/mq-deadline.c')
| -rw-r--r-- | block/mq-deadline.c | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/block/mq-deadline.c b/block/mq-deadline.c index 44da481c3fea..b09ae1f332a2 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -53,6 +53,8 @@ struct deadline_data { struct rb_root sort_list[DD_DIR_COUNT]; struct list_head fifo_list[DD_DIR_COUNT]; + /* Data direction of latest dispatched request. */ + enum dd_data_dir last_dir; /* * next in sort order. read, write or both are NULL */ @@ -179,8 +181,6 @@ deadline_move_request(struct deadline_data *dd, struct request *rq) { const enum dd_data_dir data_dir = rq_data_dir(rq); - dd->next_rq[DD_READ] = NULL; - dd->next_rq[DD_WRITE] = NULL; dd->next_rq[data_dir] = deadline_latter_request(rq); /* @@ -292,10 +292,7 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd) /* * batches are currently reads XOR writes */ - rq = deadline_next_request(dd, DD_WRITE); - if (!rq) - rq = deadline_next_request(dd, DD_READ); - + rq = deadline_next_request(dd, dd->last_dir); if (rq && dd->batching < dd->fifo_batch) /* we have a next request are still entitled to batch */ goto dispatch_request; @@ -361,6 +358,7 @@ dispatch_find_request: if (!rq) return NULL; + dd->last_dir = data_dir; dd->batching = 0; dispatch_request: @@ -473,6 +471,7 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e) dd->fifo_expire[DD_WRITE] = write_expire; dd->writes_starved = writes_starved; dd->front_merges = 1; + dd->last_dir = DD_WRITE; dd->fifo_batch = fifo_batch; spin_lock_init(&dd->lock); spin_lock_init(&dd->zone_lock); |