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Revision: 1.4
Committed: Sat Feb 21 08:27:38 2009 UTC (15 years, 4 months ago) by root
Branch: MAIN
CVS Tags: rel-0_1, HEAD
Changes since 1.3: +18 -7 lines
Log Message:
rel-0_1

File Contents

# Content
1 NAME
2 Faster - do some things faster
3
4 SYNOPSIS
5 use Faster;
6
7 perl -MFaster ...
8
9 DESCRIPTION
10 This module implements a very simple-minded "JIT" (or actually AIT,
11 ahead of time compiler). It works by more or less translating every
12 function it sees into a C program, compiling it and then replacing the
13 function by the compiled code.
14
15 As a result, startup times are immense, as every function might lead to
16 a full-blown compilation.
17
18 The speed improvements are also not great, you can expect 20% or so on
19 average, for code that runs very often. The reason for this is that data
20 handling is mostly being done by the same old code, it just gets called
21 a bit faster. Regexes and string operations won't get faster. Airhtmetic
22 doresn't become any faster. Just the operands and other stuff is put on
23 the stack faster, and the opcodes themselves have a bit less overhead.
24
25 Faster is in the early stages of development. Due to its design its
26 relatively safe to use (it will either work or simply slowdown the
27 program immensely, but rarely cause bugs).
28
29 More intelligent algorithms (loop optimisation, type inference) could
30 improve that easily, but requires a much more elaborate presentation and
31 optimiser than what is in place. There are no plans to improve Faster in
32 this way, yet, but it would provide a reasonably good place to start.
33
34 Usage is very easy, just "use Faster" and every function called from
35 then on will be compiled.
36
37 Right now, Faster can leave lots of *.c and *.so files in your
38 $FASTER_CACHEDIR (by default $HOME/.perl-faster-cache), and it will even
39 create those temporary files in an insecure manner, so watch out.
40
41 ENVIRONMENT VARIABLES
42 The following environment variables influence the behaviour of Faster:
43
44 FASTER_VERBOSE
45 Faster will output more informational messages when set to values
46 higher than 0. Currently, 1 outputs which packages are being
47 compiled, 3 outputs the cache directory and 10 outputs information
48 on which perl function is compiled into which shared object.
49
50 FASTER_DEBUG
51 Add debugging code when set to values higher than 0. Currently, this
52 adds 1-3 "assert"'s per perl op (FASTER_DEBUG > 1), to ensure that
53 opcode order and C execution order are compatible.
54
55 FASTER_CACHE
56 Set a persistent cache directory that caches compiled code
57 fragments. The default is "$HOME/.perl-faster-cache" if "HOME" is
58 set and a temporary directory otherwise.
59
60 This directory will always grow in size, so you might need to erase
61 it from time to time.
62
63 BUGS/LIMITATIONS
64 Perl will check much less often for asynchronous signals in
65 Faster-compiled code. It tries to check on every function call, loop
66 iteration and every I/O operator, though.
67
68 The following things will disable Faster. If you manage to enable them
69 at runtime, bad things will happen. Enabling them at startup will be
70 fine, though.
71
72 enabled tainting
73 enabled debugging
74
75 Thread-enabled builds of perl will dramatically reduce Faster's
76 performance, but you don't care about speed if you enable threads
77 anyway.
78
79 These constructs will force the use of the interpreter for the currently
80 executed function as soon as they are being encountered during
81 execution.
82
83 goto
84 next, redo (but not well-behaved last's)
85 labels, if used
86 eval
87 require
88 any use of formats
89 .., ... (flipflop operators)
90
91 AUTHOR
92 Marc Lehmann <schmorp@schmorp.de>
93 http://home.schmorp.de/
94