From: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
To: dev@dpdk.org
Cc: matan@mellanox.com, rasland@mellanox.com, thomas@monjalon.net,
ferruh.yigit@intel.com
Subject: [dpdk-dev] [PATCH v2] doc/mlx5: add timestamp upper limitation description
Date: Mon, 27 Jul 2020 15:51:04 +0000 [thread overview]
Message-ID: <1595865064-12892-1-git-send-email-viacheslavo@mellanox.com> (raw)
Add description about Tx scheduling timstamp upper limit.
It timstamp 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>
---
v1->v2: typo fix
doc/guides/nics/mlx5.rst | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index 90202c0..b9bd3db 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -253,6 +253,13 @@ 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`` devarog (in nanoseconds)
+ multiplied by 2^23. Please note, for the testpmd txonly testcase 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
--
1.8.3.1
next reply other threads:[~2020-07-27 15:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 15:51 Viacheslav Ovsiienko [this message]
2020-08-05 15:26 ` [dpdk-dev] [PATCH v3] doc: add timestamp upper limitation in mlx5 guide Thomas Monjalon
2020-08-05 15:43 ` Thomas Monjalon
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