[dpdk-dev] can eth_igb_xmit_pkts called with len 0 affect transmission?

[ciprian.barbu]

Anyone?

On 17.07.2015 16:48, ciprian.barbu wrote:
> Hi,
>
> I'm seeing a strange behavior when calling rte_eth_tx_burst with len ==
> 0. I'll explain the reason for this situation further bellow. But what
> I'm seeing is that after doing this call my application keeps returning
> from eth_igb_xmit_pkts here, even when len > 0:
> http://dpdk.org/browse/dpdk/tree/lib/librte_pmd_e1000/igb_rxtx.c?h=releases#n476
>
>
> I can't really explain myself this behavior, I don't understand very
> well what the nic does once it receives buffers in its rings, but to me
> it looks like calling rte_eth_tx_burst with len 0 has this effect.
>
> What I'm using in my tests is the linaro odp-dpdk implementation and the
> odp_l2fwd example. The odp-dpdk implementation makes this call to try
> and make the pmd to flush the tx queue in case there are no more free
> buffers in the pool, but this was only verified for ixgbe 82599 cards,
> for igb the packets are not actually flushed until the tail circles back
> the whole length of the queue. I'm pretty much the only one (that I know
> of) that uses odp with 1G igb i350 cards and see this issue.
>
> Can anyone explain whether I'm getting this right and there could be
> side effects to calling eth_igb_xmit_pkts with len 0?
>
> Thank you,
> /Ciprian