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

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On Sun, Sep 05, 2021 at 12:19:09PM +0300, Max Gurtovoy wrote:
> 
> On 9/5/2021 11:49 AM, Chaitanya Kulkarni wrote:
> > 
> > On 9/5/2021 12:46 AM, Leon Romanovsky wrote:
> > > > +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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