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authorReshma Pattan <reshma.pattan@intel.com>2018-10-04 13:23:59 +0100
committerThomas Monjalon <thomas@monjalon.net>2018-11-19 01:35:17 +0100
commit999aa0635c5ccd56b0ef728309d393c25aa4f5c9 (patch)
tree62fa3447f68a8c3b1b49fd43dc4c4a37aa4d440f
parenteaee9659037e7ee7c77feba76c1d940929f4a8af (diff)
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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 <longtb5@viettel.com.vn> Signed-off-by: Reshma Pattan <reshma.pattan@intel.com>
-rw-r--r--doc/guides/prog_guide/metrics_lib.rst9
1 files changed, 9 insertions, 0 deletions
diff --git a/doc/guides/prog_guide/metrics_lib.rst b/doc/guides/prog_guide/metrics_lib.rst
index 5cbe17c..e68e4e7 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.