From: Reshma Pattan Date: Thu, 4 Oct 2018 12:23:59 +0000 (+0100) Subject: doc: update timestamp validity for latency measurement X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=999aa0635c5ccd56b0ef728309d393c25aa4f5c9;p=dpdk.git doc: update timestamp validity for latency measurement Updated the doc on how packets are marked to identify their timestamp as valid and considered for latency measurement. Suggested-by: Bao-Long Tran Signed-off-by: Reshma Pattan --- diff --git a/doc/guides/prog_guide/metrics_lib.rst b/doc/guides/prog_guide/metrics_lib.rst index 5cbe17c903..e68e4e7431 100644 --- a/doc/guides/prog_guide/metrics_lib.rst +++ b/doc/guides/prog_guide/metrics_lib.rst @@ -271,3 +271,12 @@ de-initialise the latency library. .. code-block:: c rte_latencystats_uninit(); + +Timestamp and latency calculation +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The Latency stats library marks the time in the timestamp field of the +mbuf for the ingress packets and sets the ``PKT_RX_TIMESTAMP`` flag of +``ol_flags`` for the mbuf to indicate the marked time as a valid one. +At the egress, the mbufs with the flag set are considered having valid +timestamp and are used for the latency calculation.