Re: [PATCH v3 1/1] virtio-blk: add num_request_queues module parameter

On Sun, Sep 05, 2021 at 12:19:09PM +0300, Max Gurtovoy wrote:

On 9/5/2021 11:49 AM, Chaitanya Kulkarni wrote:

quoted

On 9/5/2021 12:46 AM, Leon Romanovsky wrote:

quoted

quoted

+static unsigned int num_request_queues;
+module_param_cb(num_request_queues, &queue_count_ops,
&num_request_queues,
+        0644);
+MODULE_PARM_DESC(num_request_queues,
+         "Number of request queues to use for blk device.
Should > 0");
+

Won't it limit all virtio block devices to the same limit?

It is very common to see multiple virtio-blk devices on the same system
and they probably need different limits.

Thanks

Without looking into the code, that can be done adding a configfs

interface and overriding a global value (module param) when it is set
from

configfs.

You have many ways to overcome this issue.

For example:

# ls -l /sys/block/vda/mq/
drwxr-xr-x 18 root root 0 Sep  5 12:14 0
drwxr-xr-x 18 root root 0 Sep  5 12:14 1
drwxr-xr-x 18 root root 0 Sep  5 12:14 2
drwxr-xr-x 18 root root 0 Sep  5 12:14 3

# echo virtio0 > /sys/bus/virtio/drivers/virtio_blk/unbind

# echo 8 > /sys/module/virtio_blk/parameters/num_request_queues

This is global to all virtio-blk devices.

# echo virtio0 > /sys/bus/virtio/drivers/virtio_blk/bind

# ls -l /sys/block/vda/mq/
drwxr-xr-x 10 root root 0 Sep  5 12:17 0
drwxr-xr-x 10 root root 0 Sep  5 12:17 1
drwxr-xr-x 10 root root 0 Sep  5 12:17 2
drwxr-xr-x 10 root root 0 Sep  5 12:17 3
drwxr-xr-x 10 root root 0 Sep  5 12:17 4
drwxr-xr-x 10 root root 0 Sep  5 12:17 5
drwxr-xr-x 10 root root 0 Sep  5 12:17 6
drwxr-xr-x 10 root root 0 Sep  5 12:17 7

-Max.

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