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To: Benjamin Eberlei <kontakt@beberlei.de>, PHP Internals
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Thread-Topic: [PHP-DEV] opcache.jit directive should be split up
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Date: Sat, 2 May 2020 13:59:10 +0000
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Subject: Re: [PHP-DEV] opcache.jit directive should be split up
From: tysonandre775@hotmail.com (tyson andre)

Hi Benjamin,=0A=
=0A=
> > I think it would be best to split up opcache.jit into five separate=0A=
> > configuration directives and propose the following names:=0A=
> >=0A=
> > * opcache.jit for (de)activating JIT=0A=
> > * opcache.jit_optimization_level for setting the optimization level=0A=
> > * opcache.jit_trigger for configuring the JIT trigger=0A=
> > * opcache.jit_register_allocation for configuring register allocation=
=0A=
> > * opcache.jit_cpu_flags for configuring CPU-specific flags=0A=
> >=0A=
> > ...=0A=
> =0A=
> - We now have a bool opcache.jit and the "implicit" flag=0A=
> opcache.jit_buffer_size which is 0 by default and leads to disabling the=
=0A=
> JIT. Maybe we should turn these around and set opcache.jit=3D0 and=0A=
> opcache.jit_buffer_size=3D16M (or whatever is a good default).=0A=
=0A=
I'd agree with that - I keep forgetting that `opcache.jit` isn't a boolean.=
=0A=
To avoid confusion with the RFC and to be consistent with `opcache.enable` =
and `opcache.enable_cli`,=0A=
I'd prefer `opcache.enable_jit=3D{0,1}` over `opcache.jit`.=0A=
=0A=
Also, people who are reading a php.ini would not remember what `opcache.jit=
_optimization_level=3D1` means.=0A=
Maybe supporting aliases for the 4 integer flags would be useful.=0A=
(`opcache.jit_optimization_level=3D{no,minimal,selective_inlining,jit_optim=
ize_3,jit_optimize_4,jit_optimize_5|full}`)=0A=
=0A=
- 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.=0A=
- Emit a startup error (or warn and use the default) if the alias or number=
 is unrecognized.=0A=
=0A=
One possibility I thought of is to default the `jit_buffer_size` to a multi=
ple of `opcache.memory_consumption`,=0A=
which might be a reasonable default in most use cases.=0A=
(Large codebases would get a large buffer, tiny scripts would get a small b=
uffer).=0A=
I'm not sure what that multiple should be or if there'd be a minimum that s=
hould be enforced.=0A=
=0A=
- If opcache.memory_consumption is somehow set to 0 or negative (file_cache=
_only?), maybe go with a default such as 16M.=0A=
=0A=
Thanks,=0A=
- Tyson=0A=