On Thu, 13 Oct 2016 14:35:06 +0000, Oleg Kuporosov <ol...@mellanox.com>
wrote:
> The hard requirement of financial services industry is accurate
> timestamping aligned with the packet itself. This patch is to satisfy
> this requirement:
>
> - include uint64_t timestamp field into rte_mbuf with minimal impact
> to throughput/latency. Keep it just simple uint64_t in ns (more than
> 580 years) would be enough for immediate needs while using full
> struct timespec with twice bigger size would have much stronger
> performance impact as missed cacheline0.
>
> - it is possible as there is 6-bytes gap in 1st cacheline (fast path)
> and moving uint16_t vlan_tci_outer field to 2nd cacheline.
>
> - such move will only impact for pretty rare usable VLAN RX stripping
> mode for outer TCI (it used only for one NIC i40e from the whole
> set and allows to keep minimal performance impact for RX/TX
> timestamps.
>
> Signed-off-by: Oleg Kuporosov <ol...@mellanox.com>
> ---
> lib/librte_mbuf/rte_mbuf.h | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 23b7bf8..1e1f2ed 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -851,8 +851,7 @@ struct rte_mbuf {
>
> uint32_t seqn; /**< Sequence number. See also
> rte_reorder_insert() */
> - /** Outer VLAN TCI (CPU order), valid if
> PKT_RX_QINQ_STRIPPED is set. */
> - uint16_t vlan_tci_outer;
> + uint64_t timestamp; /**< Packet's timestamp, usually
> in ns */
> /* second cache line - fields only used in slow path or on
> TX */ MARKER cacheline1 __rte_cache_min_aligned;
> @@ -885,6 +884,9 @@ struct rte_mbuf {
> };
> };
>
> + /** Outer VLAN TCI (CPU order), valid if
> PKT_RX_QINQ_STRIPPED is set. */
> + uint16_t vlan_tci_outer;
> +
> /** Size of the application private data. In case of an
> indirect
> * mbuf, it stores the direct mbuf private data size. */
> uint16_t priv_size;
FYI, I posted a RFC patchset that introduces the timestamp field in the
mbuf for v17.05:
http://dpdk.org/ml/archives/dev/2017-January/056187.html
Regards,
Olivier
