[dpdk-dev] tx_burst errors seen with virtual pmds

[Tan, Jianfeng]

Hi Souvik,

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Dey, Souvik
> Sent: Thursday, January 7, 2016 2:15 PM
> To: dev at dpdk.org
> Subject: [dpdk-dev] tx_burst errors seen with virtual pmds
> 
> Hi All,
>                 While trying call load with virtio_pmd/vmxnet3_pmd , I am seeing
> that at around 100Mbps, we are having tx_burst errors. We are currently
> using DPDK 2.1 and send 1 packet at a time. When we try the same with
> ixgbe_vf we are not seeing similar drops. Is there any issues with the virtual
> pmds which is causing  this tx drops. We are using tx descriptor as 1024 and 1
> tx queue to send out packets.
> 
> --
> Regards,
> Souvik

IMO, for virtio and vmxnet3, there's a frontend in guest and a backend in host.
And mostly, backend driver does the data copies, which spends more CPU than
frontend. So the tx descriptor queue could be always full, which leads to tx error.

Thanks,
Jianfeng