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Date: Thu, 21 Sep 2023 12:37:17 +0300
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To: Sebastian Bergmann <sebastian@php.net>
Cc: internals@lists.php.net
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Subject: Re: [PHP-DEV] [RFC] [Discussion] A new JIT implementation based on IR Framework
From: dmitrystogov@gmail.com (Dmitry Stogov)

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Hi Sebastian,

On Thu, Sep 21, 2023 at 12:22=E2=80=AFPM Sebastian Bergmann <sebastian@php.=
net>
wrote:

> Am 21.09.2023 um 11:13 schrieb Tim D=C3=BCsterhus:
> > Thank you. I find it important to follow the formal process, even if
> many
> > folks are not able to make a meaningful decision due to the lack of
> > knowledge about the topic. This includes me.
>
> I'm in the same boat.
>
> > My understanding is that even if the new JIT might not (yet) be better
> > than the old one, it is not worse and it is more maintainable. The
> > reactions from more knowledgeable folks were pretty positive overall.
>
> That is my understanding as well.
>
> > So if the new JIT passes the existing test suite without issues, I don'=
t
> > see a reason why the old JIT should not be replaced right away. By
> > immediately removing the old JIT (ideally in a separate commit) the
> > codebase is cleaned up and users that want to test PHP 8.4 (or whatever
> > that version may be in the end) will be forced to also test the new JIT
> > which is probably a good thing.
>
> I agree.
>
> As a sidenote: most of the teams that I work with use PHP 8 in production=
.
> However, none of them use the current JIT. It either caused problems
> (especially during early PHP 8.0 versions), or does not bring any
> significant performance improvement. Against that backdrop, I would be
> interested in whether you, Dmitry or Zend, can share some insight from
> real-world usage of the JIT.
>

I still don't recommend using JIT for production without serious testing
and benchmarking for each concrete case.
If you see less than 5% speedup - you probably don't need JIT; if an AMPHP
bsed server becomes 1.5 times faster it's a different story.

Thanks. Dmitry.


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