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To: "'tyson andre'" <tysonandre775@hotmail.com>,
	"'Benjamin Eberlei'" <kontakt@beberlei.de>,
	"'PHP Internals'" <internals@lists.php.net>
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Date: Sun, 3 May 2020 02:15:14 +0800
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Subject: RE: [PHP-DEV] opcache.jit directive should be split up
From: me@jhdxr.com (=?utf-8?b?Q0hVIFpoYW93ZWk=?=)

Hi Tyson,

For `opcache.jit_optimization_level` I think we'd better remain these magic
numbers, like what we did for `opcache.optimization_level`. 
I think this kind of setting requires professional knowledge in this domain,
and it doesn't make much sense to change to the text-based 
Options. E.g. what does "minimal" mean in this context? 

Regards,
CHU Zhaowei

-----Original Message-----
From: tyson andre <tysonandre775@hotmail.com> 
Sent: Saturday, May 2, 2020 9:59 PM
To: Benjamin Eberlei <kontakt@beberlei.de>; PHP Internals
<internals@lists.php.net>
Subject: Re: [PHP-DEV] opcache.jit directive should be split up

Hi Benjamin,

> > I think it would be best to split up opcache.jit into five separate 
> > configuration directives and propose the following names:
> >
> > * opcache.jit for (de)activating JIT
> > * opcache.jit_optimization_level for setting the optimization level
> > * opcache.jit_trigger for configuring the JIT trigger
> > * opcache.jit_register_allocation for configuring register 
> > allocation
> > * opcache.jit_cpu_flags for configuring CPU-specific flags
> >
> > ...
> 
> - We now have a bool opcache.jit and the "implicit" flag 
> opcache.jit_buffer_size which is 0 by default and leads to disabling 
> the JIT. Maybe we should turn these around and set opcache.jit=0 and 
> opcache.jit_buffer_size=16M (or whatever is a good default).

I'd agree with that - I keep forgetting that `opcache.jit` isn't a boolean.
To avoid confusion with the RFC and to be consistent with `opcache.enable`
and `opcache.enable_cli`, I'd prefer `opcache.enable_jit={0,1}` over
`opcache.jit`.

Also, people who are reading a php.ini would not remember what
`opcache.jit_optimization_level=1` means.
Maybe supporting aliases for the 4 integer flags would be useful.
(`opcache.jit_optimization_level={no,minimal,selective_inlining,jit_optimize
_3,jit_optimize_4,jit_optimize_5|full}`)

- I can't think of a good name for 3-5. Also, it's possible that even more
aggressive settings may be added in the future.
- Emit a startup error (or warn and use the default) if the alias or number
is unrecognized.

One possibility I thought of is to default the `jit_buffer_size` to a
multiple of `opcache.memory_consumption`, which might be a reasonable
default in most use cases.
(Large codebases would get a large buffer, tiny scripts would get a small
buffer).
I'm not sure what that multiple should be or if there'd be a minimum that
should be enforced.

- If opcache.memory_consumption is somehow set to 0 or negative
(file_cache_only?), maybe go with a default such as 16M.

Thanks,
- Tyson

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