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 <
[email protected]>
http://home.schmorp.de/
