From b5f615612ae68cbc4b64fb12d6efb4e545fcd0eb Mon Sep 17 00:00:00 2001 From: Viacheslav Ovsiienko Date: Mon, 27 Jul 2020 15:51:04 +0000 Subject: [PATCH] doc: add timestamp upper limitation in mlx5 guide Add description about Tx scheduling timestamp upper limit. If timestamp exceeds the value, it is marked by PMD as being into "too-distant-future" and not scheduled at all (is being sent without any wait). Signed-off-by: Viacheslav Ovsiienko Signed-off-by: Thomas Monjalon --- doc/guides/nics/mlx5.rst | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst index 90202c0bbb..211c0c5a6c 100644 --- a/doc/guides/nics/mlx5.rst +++ b/doc/guides/nics/mlx5.rst @@ -253,6 +253,14 @@ Limitations reported via device xstats to assist applications to detect the time-related problems. + The timestamp upper "too-distant-future" limit + at the moment of invoking the Tx burst routine + can be estimated as ``tx_pp`` option (in nanoseconds) multiplied by 2^23. + Please note, for the testpmd txonly mode, + the limit is deduced from the expression:: + + (n_tx_descriptors / burst_size + 1) * inter_burst_gap + There is no any packet reordering according timestamps is supposed, neither within packet burst, nor between packets, it is an entirely application responsibility to generate packets and its timestamps -- 2.20.1