On Tue, Aug 30, 2022 at 02:04:55PM -0700, Si-Wei Liu
wrote:>
>
> On 8/30/2022 12:58 PM, Michael S. Tsirkin wrote:
> > On Tue, Aug 30, 2022 at 06:22:31AM +0000, Eli Cohen wrote:
> > >
> > > Hi,
> > >
> > >
> > > I have been experimenting with different queue sizes with
mlx5_vdpa and noticed
> > > that queue size can affect performance.
> > >
> > > I would like to propose an extension to vdpa tool to allow to
specify the queue
> > > size. Valid values will conform to the max of 32768 specified by
the spec.
> > >
> > >
> > > ?vdpa mgmtdev show? will have another line specifying the valid
range for a
> > > management device which could be narrower than the spec allows.
This range will
> > > be valid for data queues only (not for control VQ).
> > >
> > > Another line will display the default queue size
> > >
> > >
> > > Example:
> > >
> > > $ vdpa mgmtdev show
> > >
> > > auxiliary/mlx5_core.sf.6:
> > >
> > > supported_classes net
> > >
> > > max_supported_vqs 65
> > >
> > > dev_features CSUM GUEST_CSUM MTU HOST_TSO4 HOST_TSO6 STATUS
CTRL_VQ CTRL_VLAN
> > > MQ CTRL_MAC_ADDR VERSION_1 ACCESS_PLATFORM
> > >
> > > data queue range 256-4096
> > >
> > > default queue size 256
> > >
> > >
> > > When you create the vdpa device you can specify the requested
value:
> > >
> > > $ vdpa dev add name vdpa-a mgmtdev auxiliary/mlx5_core.sf.6
max_vqp 1 mtu 9000
> > > queue_size 1024
> > >
> >
> > A follow up question: isn't it enough to control the size
> > from qemu? do we need ability to control it at the kernel level?
> >
> Right, I think today we can optionally control the queue size from qemu via
> rx_queue_size or tx_queue_size, but it has a limit of 1024 (btw why it has
> such limit, which is relatively lower in my opinion). I think what was
> missing for QEMU is to query the max number of queue size that the hardware
> can support from the backend.
>
> -Siwei
>
okay sure. my question is how important is it to control it in the
kernel?
--
MST