On Fri, Feb 17, 2017 at 1:49 PM, Nélio Laranjeiro <nelio.laranje...@6wind.com> wrote: > Hi Olivier, Jan, > > On Fri, Feb 17, 2017 at 11:51:53AM +0100, Olivier Matz wrote: >> Hi Jan, >> >> On Thu, 16 Feb 2017 18:26:39 +0100, Jan Blunck <jblu...@infradead.org> >> wrote: >> > >> > If we talk about setting the timestamp value in the RX path this >> > implicitly means software timestamps. Hardware timestamping usually >> > works by letting the hardware inject sync events for coarse time >> > tracking and additionally injecting fine granular per-packet ticks at >> > a specific offset in the packet. Out of performance reasons I don't >> > think it makes sense to extract this during the burst and write it >> > into the mbuf again. >> >> From what I've understand, at least it does not work like this for >> mellanox NICs: timestamp is a metadata attached to a rx packet. But >> maybe they (and other NIC vendors interrested in the feature) can >> confirm or not. > > Olivier is right, this timestamp information is returned by the hardware > as the other fields describing the Rx packet (length, RSS hash, checksum > ...). The PMD only copy it into the Mbuf. >
Indeed, for Mellanox the timestamp is stored in the CQ entry. Solarflares write it relative to the packet header.
