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File 2602-erts-Limit-the-automatic-max-buffer-for-UDP-to-2-16.patch of Package erlang
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: [PATCH 2/2] 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 --- erts/emulator/drivers/common/inet_drv.c | 9 ++++++++- lib/kernel/doc/src/inet.xml | 19 ++++++++++--------- lib/kernel/test/gen_udp_SUITE.erl | 12 ++++++++++-- 3 files changed, 28 insertions(+), 12 deletions(-) diff --git a/erts/emulator/drivers/common/inet_drv.c b/erts/emulator/drivers/common/inet_drv.c index 833befefd1..2048d0f625 100644 --- a/erts/emulator/drivers/common/inet_drv.c +++ b/erts/emulator/drivers/common/inet_drv.c @@ -1549,6 +1549,8 @@ static void *realloc_wrapper(void *current, ErlDrvSizeT size){ # define LOAD_ASSOC_ID LOAD_UINT # define LOAD_ASSOC_ID_CNT LOAD_UINT_CNT # define SCTP_ANC_BUFF_SIZE INET_DEF_BUFFER/2 /* XXX: not very good... */ +#else +# define IS_SCTP(desc) 0 #endif #ifdef HAVE_UDP @@ -6436,7 +6438,12 @@ static int inet_set_opts(inet_descriptor* desc, char* ptr, int len) (long)desc->port, desc->s, res)); if (type == SO_RCVBUF) { /* make sure we have desc->bufsz >= SO_RCVBUF */ - if (ival > desc->bufsz) + if (ival > (1 << 16) && desc->stype == SOCK_DGRAM && !IS_SCTP(desc)) + /* For UDP we don't want to automatically + set the buffer size to be larger than + the theoretical max MTU */ + desc->bufsz = 1 << 16; + else if (ival > desc->bufsz) desc->bufsz = ival; } } 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) >= max(val(sndbuf),val(recbuf))</c> to + Kernel socket buffers. For TCP it is recommended + to have <c>val(buffer) >= 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, recv_poll_after_active_once/1, open_fd/1, connect/1, implicit_inet6/1, local_basic/1, local_unbound/1, @@ -50,6 +50,7 @@ suite() -> send_to_closed, buffer_size, binary_passive_recv, + max_buffer_size, bad_address, read_packets, recv_poll_after_active_once, @@ -260,6 +261,14 @@ 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 -- 2.16.4
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