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From: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
To: barebox@lists.infradead.org
Cc: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
Subject: [PATCH v4 21/21] tftp: add some documentation about windowsize support
Date: Tue, 30 Aug 2022 09:38:16 +0200	[thread overview]
Message-ID: <20220830073816.2694734-22-enrico.scholz@sigma-chemnitz.de> (raw)
In-Reply-To: <20220830073816.2694734-1-enrico.scholz@sigma-chemnitz.de>

Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
---
 Documentation/filesystems/tftp.rst | 38 ++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/Documentation/filesystems/tftp.rst b/Documentation/filesystems/tftp.rst
index a292765e2511..8929213d3c4a 100644
--- a/Documentation/filesystems/tftp.rst
+++ b/Documentation/filesystems/tftp.rst
@@ -20,3 +20,41 @@ Example:
 
 In addition to the TFTP filesystem implementation, barebox does also have a
 :ref:`tftp command <command_tftp>`.
+
+RFC 7440 "windowsize" support
+=============================
+
+barebox supports the tftp windowsize option for downloading files.  It
+is not implemented for uploads.
+
+Generally, this option greatly improves the download speed (factors
+4-30 are not uncommon).  But choosing a too large windowsize can have
+the opposite effect.  Performance depends on:
+
+ - the network infrastructure: when the tftp server sends files with
+   1Gb/s but there are components in the network (switches or the
+   target nic) which support only 100 Mb/s, packets will be dropped.
+
+   The lower the internal buffers of the bottleneck components, the
+   lower the optimal window size.
+
+   In practice (iMX8MP on a Netgear GS108Ev3 with a port configured to
+   100 Mb/s) it had to be reduced to
+
+   .. code-block:: console
+     global tftp.windowsize=26
+
+   for example.
+
+ - the target network driver: datagrams from server will arive faster
+   than they can be processed and must be buffered internally.  For
+   example, the `fec-imx` driver reserves place for
+
+   .. code-block:: c
+     #define FEC_RBD_NUM		64
+
+   packets before they are dropped
+
+ - partially the workload: copying downloaded files to ram will be
+   faster than burning them into flash.  Latter can consume internal
+   buffers quicker so that windowsize might be reduced
-- 
2.37.2




  parent reply	other threads:[~2022-08-30  7:44 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-30  7:37 [PATCH v4 00/21] add "windowsize" (RFC 7440) support for tftp Enrico Scholz
2022-08-30  7:37 ` [PATCH v4 01/21] tftp: add some 'const' annotations Enrico Scholz
2022-08-30  7:37 ` [PATCH v4 02/21] tftp: allow to change tftp port Enrico Scholz
2022-08-30  7:37 ` [PATCH v4 03/21] cmd:tftp: add '-P' option to set tftp server port number Enrico Scholz
2022-08-30  7:37 ` [PATCH v4 04/21] tftp: do not set 'tsize' in WRQ requests Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 05/21] tftp: assign 'priv->block' later in WRQ Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 06/21] tftp: minor refactoring of RRQ/WRQ packet generation code Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 07/21] tftp: replace hardcoded blksize by global constant Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 08/21] tftp: remove sanity check of first block Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 09/21] tftp: add debug_assert() macro Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 10/21] tftp: allocate buffers and fifo dynamically Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 11/21] tftp: add sanity check for OACK response Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 12/21] tftp: record whether tftp file is opened for lookup operation only Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 13/21] tftp: reduce block size on lookup requests Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 14/21] tftp: refactor data processing Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 15/21] tftp: detect out-of-memory situations Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 16/21] tftp: implement 'windowsize' (RFC 7440) support Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 17/21] tftp: do not use 'priv->block' for RRQ Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 18/21] tftp: reorder tftp packets Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 19/21] tftp: add selftest Enrico Scholz
2022-08-30  7:38 ` [PATCH v4 20/21] tftp: accept OACK + DATA datagrams only in certain states Enrico Scholz
2022-08-30  7:38 ` Enrico Scholz [this message]
2022-08-31  6:40 ` [PATCH v4 00/21] add "windowsize" (RFC 7440) support for tftp Sascha Hauer

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