Re: [dpdk-dev] [RFC PATCH 3/3] net/pcap: support hardware Tx timestamps

[PATRICK KEROULAS <patrick.keroulas@radio-canada.ca>]

Hello Olivier and Slava,

On Tue, Jul 7, 2020 at 10:47 AM Olivier Matz <olivier.matz@6wind.com> wrote:
> For the pmd pcap part, the dynamic Tx timestamp flag that is being
> introduced by Slava [1] may fit your needs: ie. when the flag is set, it
> uses the provided timestamp which should be in nanosecs.
>
> [1] https://patchwork.dpdk.org/patch/73427/
>
> For the conversion from hardware Rx timestamp into Tx timestamp (in
> nanosec), could it be done by your application? Early in the Rx path, if
> a packet has a Rx timestamp flag, do the conversion to nsecs, and set
> the timestamp field and the Tx timestamp flag.

Just to be clear, we use testpmd and dpdk-pdump rather than developing
our own app. The application I mentioned earlier is a pcap analyzer and
has nothing to do with dpdk.

Could you help me identify a location where to set this dyn Tx field and flag?
My current Rx data path includes drivers/net/mlx5/mlx5_rxtx_vec_sse.h
Is it a good candidate?

For the unit conversion, I finally followed the recommendations of using
start_time & clock_freq rather than libibverbs. The time accuracy looks
similarly good, based on pcap analysis.
The conversion is performed in rte_pdump, is that acceptable?

Thanks,

PK