From 69e8387629bdea141e196c515f4d9381f7ac3e18 Mon Sep 17 00:00:00 2001 From: Magnus Henoch Date: Fri, 27 Jun 2014 17:57:04 +0100 Subject: Optimise io requests for long message queues Ensure that the monitor reference is present in all receive clauses, so that the compiler optimisation kicks in and the run time won't depend on the length of the message queue of the calling process. Remove the 'EXIT' clause, as its presence breaks the optimisation, and that case is handled by the 'DOWN' clause anyway. The test io_SUITE:io_with_huge_message_queue is an adaptation of gen_server_SUITE:call_with_huge_message_queue. --- lib/stdlib/test/io_SUITE.erl | 46 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 44 insertions(+), 2 deletions(-) (limited to 'lib/stdlib/test/io_SUITE.erl') diff --git a/lib/stdlib/test/io_SUITE.erl b/lib/stdlib/test/io_SUITE.erl index 3a76275f31..2203dd8f51 100644 --- a/lib/stdlib/test/io_SUITE.erl +++ b/lib/stdlib/test/io_SUITE.erl @@ -30,7 +30,8 @@ io_fread_newlines/1, otp_8989/1, io_lib_fread_literal/1, printable_range/1, io_lib_print_binary_depth_one/1, otp_10302/1, otp_10755/1, - otp_10836/1, io_lib_width_too_small/1]). + otp_10836/1, io_lib_width_too_small/1, + io_with_huge_message_queue/1]). -export([pretty/2]). @@ -70,7 +71,7 @@ all() -> io_fread_newlines, otp_8989, io_lib_fread_literal, printable_range, io_lib_print_binary_depth_one, otp_10302, otp_10755, otp_10836, - io_lib_width_too_small]. + io_lib_width_too_small, io_with_huge_message_queue]. groups() -> []. @@ -2219,3 +2220,44 @@ io_lib_width_too_small(Config) -> "**" = lists:flatten(io_lib:format("~2.3w", [3.14])), "**" = lists:flatten(io_lib:format("~2.5w", [3.14])), ok. + +%% Test that the time for a huge message queue is not +%% significantly slower than with an empty message queue. +io_with_huge_message_queue(Config) when is_list(Config) -> + case test_server:is_native(gen) of + true -> + {skip, + "gen is native - huge message queue optimization " + "is not implemented"}; + false -> + do_io_with_huge_message_queue(Config) + end. + +do_io_with_huge_message_queue(Config) -> + PrivDir = ?privdir(Config), + File = filename:join(PrivDir, "slask"), + {ok, F1} = file:open(File, [write]), + + {Time,ok} = timer:tc(fun() -> writes(1000, F1) end), + + [self() ! {msg,N} || N <- lists:seq(1, 500000)], + erlang:garbage_collect(), + {NewTime,ok} = timer:tc(fun() -> writes(1000, F1) end), + file:close(F1), + io:format("Time for empty message queue: ~p", [Time]), + io:format("Time for huge message queue: ~p", [NewTime]), + + IsCover = test_server:is_cover(), + case (NewTime+1) / (Time+1) of + Q when Q < 10; IsCover -> + ok; + Q -> + io:format("Q = ~p", [Q]), + ?t:fail() + end, + ok. + +writes(0, _) -> ok; +writes(N, F1) -> + file:write(F1, "hello\n"), + writes(N - 1, F1). -- cgit v1.2.3