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Date: Mon, 4 Feb 2019 20:27:15 +0100
Message-ID: <CAF+90c9WMQRZv0CE-hZ1BEORZbPuUMVRS8s5d4XyZeEjkqAmTg@mail.gmail.com>
To: Dmitry Stogov <dmitry@zend.com>
Cc: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="000000000000ef72de0581167b76"
Subject: Re: [PHP-DEV] [RFC] JIT
From: nikita.ppv@gmail.com (Nikita Popov)

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On Mon, Feb 4, 2019 at 3:44 PM Nikita Popov <nikita.ppv@gmail.com> wrote:

> On Mon, Feb 4, 2019 at 2:26 PM Dmitry Stogov <dmitry@zend.com> wrote:
>
>>
>>
>> On 2/1/19 4:23 PM, Dmitry Stogov wrote:
>> >
>> >
>> > On 2/1/19 3:09 PM, Nikita Popov wrote:
>> >> On Thu, Jan 31, 2019 at 10:44 AM Dmitry Stogov <dmitry@zend.com
>> >> <mailto:dmitry@zend.com>> wrote:
>> >>
>> >>      Hi Internals,
>> >>
>> >>
>> >>      I'm glad to finally propose including JIT into PHP.
>> >>
>> >>
>> >>      https://wiki.php.net/rfc/jit
>> >>
>> >>
>> >>      In the current state it may be included both into PHP-8, where we
>> >>      are going to continue active improvement, and into PHP-7.4, as an
>> >>      experimental feature.
>> >>
>> >>
>> >>      Thanks. Dmitry.
>> >>
>> >>
>> >> I would like to check if the JIT provides an improvement for
>> PHP-Parser.
>> >> Unfortunately I'm getting a segfault when running the tests. Should be
>> >> reproducible with
>> >>
>> >> git clone git@github.com:nikic/PHP-Parser.git
>> >> cd PHP-Parser
>> >> composer install
>> >> php-jit vendor/bin/phpunit
>> >>
>> >> I tried to debug this. Unfortunately my gdb doesn't seem to work with
>> >> JIT: It hangs when the script starts running, on line
>> Zend/zend_gdb.c:84
>> >> in zend_gdb_register_code. I don't know if that's a bug or I need to do
>> >> something additional here (I'm using GNU gdb (Ubuntu 8.1-0ubuntu3)
>> >> 8.1.0.20180409-git).
>> >
>> > GDB takes enormous time registering too many JIT-ed functions...
>> > It should be possible to catch the name of problematic functions and the
>> > JIT only them (using PHPDOC trigger). I'll try to analyze the crash, but
>> > most probably, only on next week.
>>
>> I fixed the problem caused JIT to fail on PHP-Parser tests (it was
>> related to changes introduced by typed properties patch).
>>
>> I'm also going to disable automatic JIT code registration in GDB.
>>
>> Thanks. Dmitry.
>>
>
> Thanks. I was now able to run a PHP-Parser benchmark, which showed ~1.5x
> speedup with default JIT configuration. That's promising :)
>

Unfortunately I made a mistake here and benchmarked against vanilla PHP
without opcache (and more importantly the optimizer in opcache). Here are
the correct results (for repeated parsing of a large file):

PHP: 3.7s
PHP+optimizer: 3.2s
PHP+optimizer+JIT: 2.4s

So the speedup is ~1.3x rather than ~1.5x, which is still good.

I also ran the hello-world.php example of
https://github.com/amphp/http-server against wrk -c100 -d30 -t4 and got the
following results:

PHP: 9950 rps
PHP+optimizer: 10750 rps
PHP+optimizer+JIT: 11350 rps

So in this case the improvement is about 5%. (This is the HTTP 1.1 server,
HTTP 2 would also be interesting to try, but needs some more setup.)

Nikita

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