From dbba42d8a9ebddcc1c1412e8457f79f3cb6ef6e7 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Wed, 21 Oct 2015 16:34:20 -0400 Subject: [PATCH] dm: eliminate unused "bioset" process for each bio-based DM device Commit 54efd50bfd873e2dbf784e0b21a8027ba4299a3e ("block: make generic_make_request handle arbitrarily sized bios") makes it possible for block devices to process large bios. In doing so that commit allocates a new queue->bio_split bioset for each block device, this bioset is used for allocating bios when the driver needs to split large bios. Each bioset allocates a workqueue process, thus the above commit increases the number of processes allocated per block device. DM doesn't need the queue->bio_split bioset, thus we can deallocate it. This reduces the number of allocated processes per bio-based DM device from 3 to 2. Also remove the call to blk_queue_split(), it is not needed because DM does its own splitting. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer --- drivers/md/dm.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 95558432c080..64b50b71400f 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1763,8 +1763,6 @@ static void dm_make_request(struct request_queue *q, struct bio *bio) map = dm_get_live_table(md, &srcu_idx); - blk_queue_split(q, &bio, q->bio_split); - generic_start_io_acct(rw, bio_sectors(bio), &dm_disk(md)->part0); /* if we're suspended, we have to queue this io for later */ @@ -2792,6 +2790,12 @@ int dm_setup_md_queue(struct mapped_device *md) case DM_TYPE_BIO_BASED: dm_init_old_md_queue(md); blk_queue_make_request(md->queue, dm_make_request); + /* + * DM handles splitting bios as needed. Free the bio_split bioset + * since it won't be used (saves 1 process per bio-based DM device). + */ + bioset_free(md->queue->bio_split); + md->queue->bio_split = NULL; break; } -- 2.39.2