From: Leon Romanovsky <leon@kernel.org>
To: Max Gurtovoy <mgurtovoy@nvidia.com>
Cc: Chaitanya Kulkarni <ckulkarnilinux@gmail.com>,
hch@infradead.org, mst@redhat.com,
virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
stefanha@redhat.com, israelr@nvidia.com, nitzanc@nvidia.com,
oren@nvidia.com, linux-block@vger.kernel.org, axboe@kernel.dk
Subject: Re: [PATCH v3 1/1] virtio-blk: add num_request_queues module parameter
Date: Sun, 5 Sep 2021 16:10:04 +0300 [thread overview]
Message-ID: <YTTBrD/0bHcyfNGm@unreal> (raw)
In-Reply-To: <5aada544-356f-5363-c6e4-6885e9812f82@nvidia.com>
On Sun, Sep 05, 2021 at 02:16:58PM +0300, Max Gurtovoy wrote:
>
> On 9/5/2021 1:19 PM, Leon Romanovsky wrote:
> > 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.
>
> You define a global module param but you bind/unbind a specific device.
>
> Do you have a better way to control it ?
One of the possible solutions will be to extend virtio bus to allow
setting of such pre-probe parameters. However I don't know if it is
really worth doing it,
>
> if the device is already probed, it's too late to change the queue_num.
>
>
> >
> > > # 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.
> > >
> > >
next prev parent reply other threads:[~2021-09-05 13:10 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-02 20:46 [PATCH v3 1/1] virtio-blk: add num_request_queues module parameter Max Gurtovoy
2021-09-03 6:06 ` Pankaj Gupta
2021-09-05 7:46 ` Leon Romanovsky
2021-09-05 8:49 ` Chaitanya Kulkarni
2021-09-05 9:19 ` Max Gurtovoy
2021-09-05 10:19 ` Leon Romanovsky
2021-09-05 11:16 ` Max Gurtovoy
2021-09-05 13:10 ` Leon Romanovsky [this message]
2021-09-05 13:16 ` Max Gurtovoy
2021-09-05 10:20 ` Leon Romanovsky
2021-09-05 15:15 ` Michael S. Tsirkin
2021-09-07 23:04 ` Leon Romanovsky
2021-10-22 9:30 ` Michael S. Tsirkin
2021-10-24 7:19 ` Max Gurtovoy
2021-10-24 8:12 ` Max Gurtovoy
2021-10-24 8:48 ` Michael S. Tsirkin
2021-10-24 10:57 ` Max Gurtovoy
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