linux-kernel - [PATCH 5/5] blk-mq: Lower minimum queue depth from 4 to 1

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Message-ID: <20130821152817.GC27943@dhcp-26-207.brq.redhat.com>
Date:	Wed, 21 Aug 2013 17:28:18 +0200
From:	Alexander Gordeev <agordeev@...hat.com>
To:	Jens Axboe <axboe@...nel.dk>
Cc:	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	Mike Christie <michaelc@...wisc.edu>,
	Shaohua Li <shli@...ionio.com>
Subject: [PATCH 5/5] blk-mq: Lower minimum queue depth from 4 to 1

There is no reason to limit minimum queue depth.
Indeed, some ATA devices ask for the depth of 1.

Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
---
 block/blk-mq-tag.c |    2 +-
 block/blk-mq-tag.h |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index e74e18e..a115862 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -456,7 +456,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 	tags->nr_tags = total_tags;
 	tags->reserved_tags = reserved_tags;
 	tags->max_cache = nr_cache;
-	tags->batch_move = nr_cache / 2;
+	tags->batch_move = max(1u, nr_cache / 2);
 
 	/*
 	 * Reserved tags are first
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 716ea79..947ba2c 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -14,7 +14,7 @@ extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags);
 extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page);
 
 enum {
-	BLK_MQ_TAG_CACHE_MIN	= 4,
+	BLK_MQ_TAG_CACHE_MIN	= 1,
 	BLK_MQ_TAG_CACHE_MAX	= 64,
 };
 
-- 
1.7.7.6

-- 
Regards,
Alexander Gordeev
agordeev@...hat.com
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