Re: [PATCH] Increase the tx queue to 512 descriptors to fix performance problem.

[Anthony Liguori <aliguori@us.ibm.com>]

Dor Laor wrote:
> Now that we have a host timer based tx wakeup it waits for 64
> packets or timeout before processing them.
> This might cause the guest to run out of tx buffers while the host
> holds them up.
>   

There's a proper fix that Rusty added last night.

> This is a temporal solution to quickly bring back performance to 800mbps.
> But a better fix will soon be sent (its not the only problem).
>   

How are you doing performance testing?

Regards,

Anthony Liguori

> Signed-off-by: Dor Laor <dor.laor@qumranet.com>
> ---
>  qemu/hw/virtio-net.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/qemu/hw/virtio-net.c b/qemu/hw/virtio-net.c
> index 777fe2c..3d07b65 100644
> --- a/qemu/hw/virtio-net.c
> +++ b/qemu/hw/virtio-net.c
> @@ -293,7 +293,7 @@ void *virtio_net_init(PCIBus *bus, NICInfo *nd, int devfn)
>      n->vdev.update_config = virtio_net_update_config;
>      n->vdev.get_features = virtio_net_get_features;
>      n->rx_vq = virtio_add_queue(&n->vdev, 512, virtio_net_handle_rx);
> -    n->tx_vq = virtio_add_queue(&n->vdev, 128, virtio_net_handle_tx);
> +    n->tx_vq = virtio_add_queue(&n->vdev, 512, virtio_net_handle_tx);
>      n->can_receive = 0;
>      memcpy(n->mac, nd->macaddr, 6);
>      n->vc = qemu_new_vlan_client(nd->vlan, virtio_net_receive,
>