Re: ixgbe TX function selection

[Zoltan Kiss <zoltan.kiss@linaro.org>]

On 10/03/16 07:51, Wu, Jingjing wrote:
> Hi, Zoltan
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Zoltan Kiss
>> Sent: Wednesday, March 2, 2016 3:19 AM
>> To: dev@dpdk.org
>> Subject: [dpdk-dev] ixgbe TX function selection
>>
>> Hi,
>>
>> I've noticed that ixgbe_set_tx_function() selects the non-SG function
>> even if (dev->data->scattered_rx == 1). That seems a bit dangerous, as
>> you can turn that on inadvertently when you don't set max_rx_pkt_len and
>> buffer size in certain ways. I've learnt it in the hard way, as my
>> segmented packets were leaking memory on the TX path, which doesn't
>> cries if you send out segmented packets.
>> How should this case be treated? Assert on the non-SG TX side for the
>> 'next' pointer? Or turning on SG if RX has it? It doesn't seem to be a
>> solid way as other interfaces still can have SG turned on.
>>
>
> If you look into the ixgbe_set_tx_function, you will find tx function
> selection is decided by the tx_flags on queue configure, which is
> passed by rte_eth_txconf. So even you set dev->data->scattered_rx to 1,
> if the tx_flags is ETH_TXQ_FLAGS_NOMULTSEGS, ixgbe_xmit_pkts_simple is
> still selected as tx function. So, you'd better to set tx_flags=0, and have a try.

You mean getting default_txconf from rte_eth_dev_info_get() and 
explicitly turn ETH_TXQ_FLAGS_NOMULTSEGS to 0? (filling tx_flags with 
zeros doesn't work very well) That's a way to solve it for me, but I'm 
rather talking about using defaults which doesn't cause memory leak 
quite easily.

>
>> Regards,
>>
>> Zoltan