[ofa-general] IB Packet receive timings

[Dotan Barak]

Adit Ranadive wrote:
> Hello,
>
> I had a question on whether it is possible to get the exact timing at
> which a packet arrived in the recieve queue on the HCA?
> Does the packet have a timestamp which the HCA modifies when it
> arrives? If so, how can one retrieve this?
>   
I think that getting this info is impossible.

For example: a message of 2 GB was received (with several packet 
retransmission).
Which timestamps will be created: for all of the packets or only for the 
first/last one?
where will they be written in?

For this message a single completion may be created (if this was a SEND 
operation and not an RDMA).


Maybe HW vendors can supply this info using special registers/commands, 
but there isn't any standard way to
get this info.


The closest thing that you can do is to query the IB port counters for 
received packets and received data
(for example, the utility perfquery give you the values of those counters).


Dotan