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Date: Wed, 10 Apr 2013 16:16:34 +0300
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To: Arvids Godjuks <arvids.godjuks@gmail.com>
Cc: PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] OPcache optimizer improvement in PHP-5.5?
From: florinpatan@gmail.com (Florin Patan)

>On Wed, Apr 10, 2013 at 4:07 PM, Arvids Godjuks <arvids.godjuks@gmail.com> wrote:
> 2013/4/10 Dmitry Stogov <dmitry@zend.com>
>
>> Hi,
>>
>> Recently, I've found that OPcache optimizer misses a lot of abilities,
>> because it handles only one op_array at once. So it definitely can't
>> perform any inter-function optimizations (e.g. inlining).
>>
>> Actually, it was not very difficult to switch to "script at once" approach.
>> The attached patch demonstrates it and adds per script constants
>> substitution explained in the following script
>>
>> <?php
>> define("FOO", 1);
>> function foo() {
>>     echo FOO . "\n"; // optimizer will replace it with: echo "1\n";
>> }
>> ?>
>>
>> Of course, I ran the PHP test suite and it passed all the same tests.
>> Personally, I think it's safe to include this patch into 5.5 and make a
>> green light to some other advanced optimizations in 5.5. (e.g. conversion
>> INIT_FCALL_BY_NAME into DO_FCALL).
>>
>> Any thoughts?
>>
>> Thanks. Dmitry.
>>
>> --
>> PHP Internals - PHP Runtime Development Mailing List
>> To unsubscribe, visit: http://www.php.net/unsub.php
>>
>
>
> Hi!
>
> Many obvious optimizations are not used due to the fact, that script
> translation into opcode state has to be fast. The nature of PHP dictated
> that and this was re-iterated countless times on this mailing list by the
> core developers.
>
> To do advanced stuff, you have to create some sort of pre-compile or
> storing that compiled code reliably on disk so that if memory cache is
> dropped or restart is done, there is no significant preformance hit while
> all the code compiles into optimized opcode again.
>
> I would also imagine that good part of the optimizations would require
> multiple files to be processed and optimized, but due to dynamic nature of
> the PHP opcode compilation is done on per-file basis, so do the
> optimizations.
>
> It's very commendable that you want to push optimizations and stuff, but
> there are some fundamental stuff that needs to be cared of to do some
> really good stuff.
>
> My 0.02$

Hello,


If applying optimizations in multiple passes would be a problem for
speed, especially on the first request, then maybe a way to solve this
would be to have a configurable variable like: opcache.passes which is
between 1 and 10 (lets say) and then have the engine do something like
this:
- load the file, compile it and apply a first round of 'quick'
optimizations for the first time and mark it as passed once;
- next request, load the compiled version, apply another round of
optimization then mark it as a second pass
- repeat the above step until the optimization passes in the said file
= opcache.passes value

This way only the initial requests will be affected by this but in a
way that the hit on those requests is smaller that applying all the
steps at once.
I'm really not sure if it's that easy to implement but 'on paper' this
could be the way to solve it imho.

What do you think, does it make sense?



Best regards
----
Florin Patan
https://github.com/dlsniper
http://www.linkedin.com/in/florinpatan