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Date: Fri, 27 Feb 2015 19:39:29 +0200
Message-ID: <63262a9c0edd51bbf38df2a00c87340e@mail.gmail.com>
To: Dmitry Stogov <dmitry@zend.com>, Anthony Ferrara <ircmaxell@gmail.com>
Cc: Jordi Boggiano <j.boggiano@seld.be>, PHP Internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: RE: [PHP-DEV] Re: Zend JIT Open Sourced
From: zeev@zend.com (Zeev Suraski)

> -----Original Message-----
> From: Dmitry Stogov [mailto:dmitry@zend.com]
> Sent: Friday, February 27, 2015 7:31 PM
> To: Anthony Ferrara
> Cc: Jordi Boggiano; PHP Internals
> Subject: Re: [PHP-DEV] Re: Zend JIT Open Sourced
>
> On Fri, Feb 27, 2015 at 7:30 PM, Anthony Ferrara <ircmaxell@gmail.com>
> wrote:
>
> > Dmitry,
> >
> >
> > > It's not a single request cycle. JIT integrated into opcache, it
> > > compiles php script(s) of first access and stores code in shared
> > > memory.
> > > On following requests precompiled code is executed directly from
> > > shared memory.
> > >
> > > - The first request may be extremely slow (few minutes)
> >
> > That sounds more along the lines of AOT like I did with Recki rather
> > than a true JIT (which compiles when a function is called).
> >
> > Judging from the jit_init() function, it appears like you're compiling
> > the entire codebase ahead of time.
> >
> > Is that correct?
> >
>
> Right now it compiles script (php file) at once.
> So yes, our JIT uses some kind of AOT approach, but completely
> transparently for the rest of PHP.

Just to slightly further clarify - we don't compile the whole codebase at
once, but we keep the existing semantics that every file is independent, may
change independently of other files, and include() may end up load one file
in one flow and another one in another flow.  There's isn't any cross-file
optimization.

> We also tried few different approaches to collect formation about hot
> functions and generate code only for them.
> Unfortunately, this didn't change the picture.

(again, the picture being no performance gains in common Web apps).

Zeev