From a9d361b4be7d6329bedd7b37d454c1abf4f27233 Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang.org>
Date: Thu, 21 Jun 2018 11:00:25 +0200
Subject: erts: Limit the automatic max buffer for UDP to 2^16

There is no reason to have a larger buffer than this as
the recvmsg call will never return more data.

OTP-15206
---
 lib/kernel/doc/src/inet.xml | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

(limited to 'lib/kernel/doc/src')

diff --git a/lib/kernel/doc/src/inet.xml b/lib/kernel/doc/src/inet.xml
index e6a7962c5a..f281d61459 100644
--- a/lib/kernel/doc/src/inet.xml
+++ b/lib/kernel/doc/src/inet.xml
@@ -734,22 +734,23 @@ get_tcpi_sacked(Sock) ->
           </item>
           <tag><c>{buffer, Size}</c></tag>
           <item>
-            <p>The size of the user-level software buffer used by
-              the driver. 
-              Not to be confused with options <c>sndbuf</c>
+            <p>The size of the user-level buffer used by
+              the driver. Not to be confused with options <c>sndbuf</c>
               and <c>recbuf</c>, which correspond to the
-              Kernel socket buffers. It is recommended
-              to have <c>val(buffer) &gt;= max(val(sndbuf),val(recbuf))</c> to
+              Kernel socket buffers. For TCP it is recommended
+              to have <c>val(buffer) &gt;= val(recbuf)</c> to
               avoid performance issues because of unnecessary copying.
+              For UDP the same recommendation applies, but the max should
+              not be larger than the MTU of the network path.
               <c>val(buffer)</c> is automatically set to the above
-              maximum when values <c>sndbuf</c> or <c>recbuf</c> are set.
-              However, as the sizes set for <c>sndbuf</c> and <c>recbuf</c>
+              maximum when <c>recbuf</c> is set.
+              However, as the size set for <c>recbuf</c>
               usually become larger, you are encouraged to use
               <seealso marker="#getopts/2"><c>getopts/2</c></seealso>
               to analyze the behavior of your operating system.</p>
             <p>Note that this is also the maximum amount of data that can be
-	       received from a single recv call. If you are using higher than 
-	       normal MTU consider setting buffer higher.</p> 
+	       received from a single recv call. If you are using higher than
+	       normal MTU consider setting buffer higher.</p>
           </item>
           <tag><c>{delay_send, Boolean}</c></tag>
           <item>
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