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Date: Thu, 24 May 2012 11:24:17 -0400
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To: PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] php interpreter
From: tom@punkave.com (Tom Boutell)

(I'm not questioning that APC makes an enormous difference. That's
painfully obvious from 100 miles away on our servers (: )

On Thu, May 24, 2012 at 11:23 AM, Tom Boutell <tom@punkave.com> wrote:
> I've seen this statement before about the impact of caching the actual
> compilation (or mere tokenization?) to bytecode being very small
> compared to the impact of avoiding disk access. I am curious if there
> are any measurements breaking this down. Read-only access to code in
> files already buffered by the OS (not files read for the first time)
> ought to be very fast.
>
> On Tue, May 22, 2012 at 11:00 AM, Richard Lynch <ceo@l-i-e.com> wrote:
>> 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 ( $source_code =3D in_cache($path)){
>> }
>> else{
>> =A0//super-duper slow!!!
>> =A0$source_code =3D file_get_contents($path);
>> }
>> $bytecode =3D zend_parse($source_code);
>> zend_execute($bytecode);
>>
>> //save hitting the hard disk
>> //and a small bonus, cache the bytecode, not source:
>>
>> if ($bytecode =3D in_cache($path)){
>> =A0//do nothing
>> }
>> else{
>> =A0$source_code =3D file_get_contents($path);
>> =A0$bytecode =3D 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 :-)
>>
>> --
>> brain cancer update:
>> http://richardlynch.blogspot.com/search/label/brain%20tumor
>> Donate:
>> https://www.paypal.com/cgi-bin/webscr?cmd=3D_s-xclick&hosted_button_id=
=3DFS9NLTNEEKWBE
>>
>>
>>
>> --
>> PHP Internals - PHP Runtime Development Mailing List
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>>
>
>
>
> --
> Tom Boutell
> P'unk Avenue
> 215 755 1330
> punkave.com
> window.punkave.com



--=20
Tom Boutell
P'unk Avenue
215 755 1330
punkave.com
window.punkave.com