NAME
XSConfig - Fast XS drop-in replacement for Config.pm with perfect hashing.
VERSION
Version 6.11
SYNOPSIS
The Config.pm included by default with Perl is pure Perl. Nearly all Perl apps will load Config.pm. For a number of reasons, of speed and memory space, reimplement the P5P shipped Config.pm as an XS library, shareable between processes as read-only memory, and with a hash that is better optimized than Perl hashes, courtesy of gperf tool which generates collision-free perfect hashes.
This module is a drop-in replacement for Config.pm. All code that does
use Config;
will use the XS implementation after installing this module. To revert to the original pure perl Config.pm, go and delete the following 3 files that will be next to each other in /site, Config.pm, Config_mini.pl, Config_xs_heavy.pl, and the Config shared library in /auto, after deleting the /site files, the original pure perl Config.pm in /lib will be loaded.
Since XS Config is a compiled C shared library, it can not be edited with a text editor after it is built. To change the values in the XS Config module, edit the pure perl Config_heavy.pl file with a text editor and rebuild XS Config.
IT IS HIGHLY RECOMMENDED THAT YOU HAVE GPERF TOOL INSTALLED AND RUNNABLE FROM YOUR PATH BEFORE INSTALLING XS CONFIG.
BENCHMARKS
perl -MXSLoader -MConfig -e"sleep 1000"
Memory Usage KB Total Image Committed Image Private Heap Private
With PP Config 36,976 11,376 272 668
With XS Config 37,188 11,492 280 640
Using XSConfig 6.11, with a VC 2013 32 bit threaded perl, you save 20 KB of per process memory, in exchange for 108 KB of shared between process, memory mapped (Config.dll) memory. That is an increase in memory usage of 88 KB if you have just a single perl process ever running on the machine at a time, but around 4 perl processes with XS Config, XS Config uses less memory than the equivelent group of perl processes with PP Config.
The total size of Config.dll in memory is 116 KB, with 8 KB of unshareable memory, the rest is shared. The smallest (no XSUBs except boot) Win32 XS DLL without taking special measures is 24 KB, with 8 KB of unshareable memory. So around ~24 KB is the overhead of a Visual C 2013 DLL with all the C compiler specific hidden static linked functions inside the DLL (these can be removed, but it is "special measures" that aren't typical on Win32 Perls).
Onto performance, to slurp the entire tied %Config hash into a non-tied hash, with XS Config is %36 faster than with PP Config. To read 1 key in the tied %Config hash is 15% faster than with PP Config.
Raw data with XS Config
C:\sources>timeit -f t.dat perl -MXSLoader -MConfig -e"print
$Config::VERSION.\"\n\";my %h; %h = %Config for 0..1000"
6.11
Version Number: Windows NT 6.1 (Build 7601)
Exit Time: 4:32 pm, Tuesday, January 19 2016
Elapsed Time: 0:00:10.296
Process Time: 0:00:10.249
System Calls: 27201
Context Switches: 3953
Page Faults: 3497
Bytes Read: 94500
Bytes Written: 97108
Bytes Other: 13422
C:\sources>timeit -f t.dat perl -MXSLoader -MConfig -e"print
$Config::VERSION.\"\n\";my $v; $v = $Config{'ccflags'} for 0..1000000;print
$v"
6.11
-nologo -GF -W3 -O1 -MD -Zi -DNDEBUG -GL -DWIN32 -D_CONSOLE -DNO_STRICT -D_CRT_S
ECURE_NO_DEPRECATE -D_CRT_NONSTDC_NO_DEPRECATE -DPERL_TEXTMODE_SCRIPTS -DPERL_I
MPLICIT_CONTEXT -DPERL_IMPLICIT_SYS
Version Number: Windows NT 6.1 (Build 7601)
Exit Time: 4:32 pm, Tuesday, January 19 2016
Elapsed Time: 0:00:05.226
Process Time: 0:00:05.226
System Calls: 12385
Context Switches: 1843
Page Faults: 2226
Bytes Read: 91738
Bytes Written: 0
Bytes Other: 7528
With PP Config
C:\sources>timeit -f t.dat perl -MXSLoader -MConfig -e"print
$Config::VERSION.\"\n\";my %h; %h = %Config for 0..1000"
5.023005
Version Number: Windows NT 6.1 (Build 7601)
Exit Time: 4:33 pm, Tuesday, January 19 2016
Elapsed Time: 0:00:16.068
Process Time: 0:00:16.005
System Calls: 42186
Context Switches: 5417
Page Faults: 4607
Bytes Read: 136490
Bytes Written: 0
Bytes Other: 22281
C:\sources>timeit -f t.dat perl -MXSLoader -MConfig -e"print
$Config::VERSION.\"\n\";my $v; $v = $Config{'ccflags'} for 0..1000000;print
$v"
5.023005
-nologo -GF -W3 -O1 -MD -Zi -DNDEBUG -GL -DWIN32 -D_CONSOLE -DNO_STRICT -D_CRT_S
ECURE_NO_DEPRECATE -D_CRT_NONSTDC_NO_DEPRECATE -DPERL_TEXTMODE_SCRIPTS -DPERL_I
MPLICIT_CONTEXT -DPERL_IMPLICIT_SYS
Version Number: Windows NT 6.1 (Build 7601)
Exit Time: 4:33 pm, Tuesday, January 19 2016
Elapsed Time: 0:00:06.146
Process Time: 0:00:06.130
System Calls: 15062
Context Switches: 2248
Page Faults: 2381
Bytes Read: 131566
Bytes Written: 0
Bytes Other: 8414
C:\sources>
AUTHOR
Daniel Dragan <BULKDD at cpan.org>
Reini Urban <rurban at cpanel.net>
LICENSE AND COPYRIGHT
Copyright (C) 2015, Daniel Dragan Copyright (C) 2015, cPanel Inc
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.