[ViewVC] Annotation of: cvs/Faster/README

NAME
    Faster - do some things faster

SYNOPSIS
     use Faster;

     perl -MFaster ...

DESCRIPTION
    This module implements a very simple-minded "JIT" (or actually AIT,
    ahead of time compiler). It works by more or less translating every
    function it sees into a C program, compiling it and then replacing the
    function by the compiled code.

    As a result, startup times are immense, as every function might lead to
    a full-blown compilation.

    The speed improvements are also not great, you can expect 20% or so on
    average, for code that runs very often. The reason for this is that data
    handling is mostly being done by the same old code, it just gets called
    a bit faster. Regexes and string operations won't get faster. Airhtmetic
    doresn't become any faster. Just the operands and other stuff is put on
    the stack faster, and the opcodes themselves have a bit less overhead.

    Faster is in the early stages of development. Due to its design its
    relatively safe to use (it will either work or simply slowdown the
    program immensely, but rarely cause bugs).

    More intelligent algorithms (loop optimisation, type inference) could
    improve that easily, but requires a much more elaborate presentation and
    optimiser than what is in place. There are no plans to improve Faster in
    this way, yet, but it would provide a reasonably good place to start.

    Usage is very easy, just "use Faster" and every function called from
    then on will be compiled.

    Right now, Faster can leave lots of *.c and *.so files in your
    $FASTER_CACHEDIR (by default $HOME/.perl-faster-cache), and it will even
    create those temporary files in an insecure manner, so watch out.

ENVIRONMENT VARIABLES
    The following environment variables influence the behaviour of Faster:

    FASTER_VERBOSE
        Faster will output more informational messages when set to values
        higher than 0. Currently, 1 outputs which packages are being
        compiled, 3 outputs the cache directory and 10 outputs information
        on which perl function is compiled into which shared object.

    FASTER_DEBUG
        Add debugging code when set to values higher than 0. Currently, this
        adds 1-3 "assert"'s per perl op (FASTER_DEBUG > 1), to ensure that
        opcode order and C execution order are compatible.

    FASTER_CACHE
        Set a persistent cache directory that caches compiled code
        fragments. The default is "$HOME/.perl-faster-cache" if "HOME" is
        set and a temporary directory otherwise.

        This directory will always grow in size, so you might need to erase
        it from time to time.

BUGS/LIMITATIONS
    Perl will check much less often for asynchronous signals in
    Faster-compiled code. It tries to check on every function call, loop
    iteration and every I/O operator, though.

    The following things will disable Faster. If you manage to enable them
    at runtime, bad things will happen. Enabling them at startup will be
    fine, though.

     enabled tainting
     enabled debugging

    Thread-enabled builds of perl will dramatically reduce Faster's
    performance, but you don't care about speed if you enable threads
    anyway.

    These constructs will force the use of the interpreter for the currently
    executed function as soon as they are being encountered during
    execution.

     goto
     next, redo (but not well-behaved last's)
     labels, if used
     eval
     require
     any use of formats
     .., ... (flipflop operators)

AUTHOR
     Marc Lehmann <schmorp@schmorp.de>
     http://home.schmorp.de/

Revision:	1.4
Committed:	Sat Feb 21 08:27:38 2009 UTC (15 years, 2 months ago) by root
Branch:	MAIN
CVS Tags:	rel-0_1, HEAD
Changes since 1.3:	+18 -7 lines
Log Message:	rel-0_1
#	User	Rev	Content
1	root	1.1	NAME
2	root	1.2	Faster - do some things faster
3	root	1.1
4			SYNOPSIS
5	root	1.2	use Faster;
6
7			perl -MFaster ...
8	root	1.1
9			DESCRIPTION
10	root	1.4	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	root	1.2
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	root	1.4	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	root	1.2
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	root	1.4	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	root	1.2	Usage is very easy, just "use Faster" and every function called from
35			then on will be compiled.
36
37	root	1.4	Right now, Faster can leave lots of .c and .so files in your
38	root	1.3	$FASTER_CACHEDIR (by default $HOME/.perl-faster-cache), and it will even
39			create those temporary files in an insecure manner, so watch out.
40
41			ENVIRONMENT VARIABLES
42			The following environment variables influence the behaviour of Faster:
43
44			FASTER_VERBOSE
45			Faster will output more informational messages when set to values
46			higher than 0. Currently, 1 outputs which packages are being
47			compiled, 3 outputs the cache directory and 10 outputs information
48			on which perl function is compiled into which shared object.
49
50			FASTER_DEBUG
51			Add debugging code when set to values higher than 0. Currently, this
52	root	1.4	adds 1-3 "assert"'s per perl op (FASTER_DEBUG > 1), to ensure that
53			opcode order and C execution order are compatible.
54	root	1.3
55			FASTER_CACHE
56			Set a persistent cache directory that caches compiled code
57			fragments. The default is "$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	root	1.2
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	root	1.3	at runtime, bad things will happen. Enabling them at startup will be
70			fine, though.
71	root	1.2
72			enabled tainting
73			enabled debugging
74
75	root	1.3	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	root	1.2
83			goto
84			next, redo (but not well-behaved last's)
85	root	1.4	labels, if used
86	root	1.2	eval
87			require
88			any use of formats
89	root	1.3	.., ... (flipflop operators)
90	root	1.1
91			AUTHOR
92			Marc Lehmann <schmorp@schmorp.de>
93			http://home.schmorp.de/
94