21 Feb 2009 08:28:15 UTC
- Distribution: Faster
- Module version: 0.1
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- Latest versionMLEHMANN Marc A. Lehmann
Faster - do some things faster
use Faster; perl -MFaster ...
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 Fasterand 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.
The following environment variables influence the behaviour of Faster:
Faster will output more informational messages when set to values higher than
1outputs which packages are being compiled,
3outputs the cache directory and
10outputs information on which perl function is compiled into which shared object.
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.
Set a persistent cache directory that caches compiled code fragments. The default is
HOMEis set and a temporary directory otherwise.
This directory will always grow in size, so you might need to erase it from time to time.
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)
Marc Lehmann <email@example.com> http://home.schmorp.de/