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
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