On Wed, May 9, 2012 5:05 pm, Xin Tong wrote:
> I am new to php runtime. i am doing some research on runtime
> interpreter. can anyone please tell me where the interpreter of the
> php runtime is ? which file ? and does the php runtime has a JIT
> compiler ?
I believe the interpreter is built out of bison/yacc files, so you
could start with those to find out where they put it.
The php runtime is a JIT parser/compiler to a bytecode, which is then
run by the Zend Engine (see above).
Actually, that last statement might imply the the zend directory would
also be a good place to look.
Finally, it should be noted that APC and other caching mechanisms save
a great deal of time by not hitting the disk to load the script, but
keeping it in RAM, if possible.
As "gravy" on top of that, the bytecode is saved in cache instead of
source, so it is not a JIT if one of those caches is in use.
Psuedo code to describe the difference the APC (or other cache) makes:
//save hitting the hard disk
if ( $source_code = in_cache($path)){
}
else{
//super-duper slow!!!
$source_code = file_get_contents($path);
}
$bytecode = zend_parse($source_code);
zend_execute($bytecode);
//save hitting the hard disk
//and a small bonus, cache the bytecode, not source:
if ($bytecode = in_cache($path)){
//do nothing
}
else{
$source_code = file_get_contents($path);
$bytecode = zend_parse($source_code);
}
zend_execute($bytecode);
The savings from parsing is chump change compared to disk I/O.
It's also trivial chump change to implement.
Ever ounce counts :-)
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