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-rw-r--r--lib/kernel/doc/src/inet.xml19
-rw-r--r--lib/kernel/test/gen_udp_SUITE.erl12
2 files changed, 20 insertions, 11 deletions
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>
diff --git a/lib/kernel/test/gen_udp_SUITE.erl b/lib/kernel/test/gen_udp_SUITE.erl
index b39399b18a..3acfff929e 100644
--- a/lib/kernel/test/gen_udp_SUITE.erl
+++ b/lib/kernel/test/gen_udp_SUITE.erl
@@ -34,7 +34,7 @@
-export([init_per_testcase/2, end_per_testcase/2]).
-export([send_to_closed/1, active_n/1,
- buffer_size/1, binary_passive_recv/1, bad_address/1,
+ buffer_size/1, binary_passive_recv/1, max_buffer_size/1, bad_address/1,
read_packets/1, open_fd/1, connect/1, implicit_inet6/1,
local_basic/1, local_unbound/1,
local_fdopen/1, local_fdopen_unbound/1, local_abstract/1]).
@@ -44,7 +44,7 @@ suite() ->
{timetrap,{minutes,1}}].
all() ->
- [send_to_closed, buffer_size, binary_passive_recv,
+ [send_to_closed, buffer_size, binary_passive_recv, max_buffer_size,
bad_address, read_packets, open_fd, connect,
implicit_inet6, active_n,
{group, local}].
@@ -237,6 +237,14 @@ buffer_size_server_recv(Socket, IP, Port, Cnt) ->
end.
+%%-------------------------------------------------------------
+%% OTP-15206: Keep buffer small for udp
+%%-------------------------------------------------------------
+max_buffer_size(Config) when is_list(Config) ->
+ {ok, Socket} = gen_udp:open(0, [binary]),
+ ok = inet:setopts(Socket,[{recbuf, 1 bsl 20}]),
+ {ok, [{buffer, 65536}]} = inet:getopts(Socket,[buffer]),
+ gen_udp:close(Socket).
%%-------------------------------------------------------------
%% OTP-3823 gen_udp:recv does not return address in binary mode