diff mbox series

[v3] doc: add timestamp upper limitation in mlx5 guide

Message ID 20200805152610.277087-1-thomas@monjalon.net (mailing list archive)
State Accepted, archived
Delegated to: Thomas Monjalon
Headers
Series [v3] doc: add timestamp upper limitation in mlx5 guide |

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/Intel-compilation success Compilation OK
ci/travis-robot success Travis build: passed

Commit Message

Thomas Monjalon Aug. 5, 2020, 3:26 p.m. UTC 
  From: Viacheslav Ovsiienko <viacheslavo@mellanox.com>

Add description about Tx scheduling timestamp upper limit.
If timestamp exceed 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 <viacheslavo@mellanox.com>
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
---
v2: typo fix
v3: more typos fixed and small rewording
---
 doc/guides/nics/mlx5.rst | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Thomas Monjalon Aug. 5, 2020, 3:43 p.m. UTC | #1 
05/08/2020 17:26, Thomas Monjalon:
> From: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> 
> Add description about Tx scheduling timestamp upper limit.
> If timestamp exceed 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 <viacheslavo@mellanox.com>
> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> ---
> v2: typo fix
> v3: more typos fixed and small rewording

Applied
diff mbox series

Patch

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