linux-kernel - [PATCH] virtio-blk: make the queue depth configurable

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Message-Id: <1394818263-29947-1-git-send-email-tytso@mit.edu>
Date:	Fri, 14 Mar 2014 13:31:03 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Linux Kernel Developers List <linux-kernel@...r.kernel.org>
Cc:	Theodore Ts'o <tytso@....edu>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	virtio-dev@...ts.oasis-open.org,
	virtualization@...ts.linux-foundation.org, fes@...gle.com
Subject: [PATCH] virtio-blk: make the queue depth configurable

The current virtio block sets a queue depth of 64.  With a
sufficiently fast device, using a queue depth of 256 can double the
IOPS which can be sustained.  So make the queue depth something which
can be set at module load time or via a kernel boot-time parameter.

Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Cc: Rusty Russell <rusty@...tcorp.com.au>
Cc: "Michael S. Tsirkin" <mst@...hat.com>
Cc: virtio-dev@...ts.oasis-open.org
Cc: virtualization@...ts.linux-foundation.org
Cc: fes@...gle.com
---
 drivers/block/virtio_blk.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 6a680d4..0c9e57f 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -481,6 +481,9 @@ static struct blk_mq_ops virtio_mq_ops = {
 	.free_hctx	= blk_mq_free_single_hw_queue,
 };
 
+static int queue_depth = 64;
+module_param(queue_depth, int, 444);
+
 static struct blk_mq_reg virtio_mq_reg = {
 	.ops		= &virtio_mq_ops,
 	.nr_hw_queues	= 1,
@@ -551,6 +554,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 		goto out_free_vq;
 	}
 
+	virtio_mq_reg.queue_depth = queue_depth;
 	virtio_mq_reg.cmd_size =
 		sizeof(struct virtblk_req) +
 		sizeof(struct scatterlist) * sg_elems;
-- 
1.9.0

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