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[RFC] opcache.no_cache: Opcache optimization without any caching

php.internals

tyson andre

6 years ago

Hi internals,

I've created the RFC https://wiki.php.net/rfc/opcache.no_cache to make the opcode optimizer and JIT available without opcode caching, through a new setting `opcache.no_cache=1`.

So far, the feedback I've gotten is that having the ability to optimize without caching would be useful,
but that moving the optimizer into Zend is possibly a better solution.
(https://github.com/php/php-src/pull/5504 , 
announced two weeks ago in https://externals.io/message/109959 
"opcache.no_cache prototype: Opcode optimization without caching")

To summarize my reasons for creating the RFC without moving the optimizer:

- Even with the optimizer moved into PHP's core,
  I still think there'd be the same use case for a system ini configuration setting to disable caching.
  (in designs I can imagine)
- I consider this useful functionality to have, so I'd rather have a good solution than an ideal solution
  that currently isn't being worked on (to my knowledge)
- I'd prefer creating an RFC with small changes here.
- The discussions would be useful for future RFCs in this area.

If a viable RFC&implementation to move opcache into core is created
(and would conflict with this), I'll postpone this RFC.

Thanks,
- Tyson

Derick Rethans

6 years ago

On Sat, 16 May 2020, tyson andre wrote:

> I've created the RFC https://wiki.php.net/rfc/opcache.no_cache to make
> the opcode optimizer and JIT available without opcode caching, through
> a new setting `opcache.no_cache=1`.

In my opinion, configuration names should never be "in the negative".
Instead of defaulting to opcache.no_cache=0, default to opcache.cache=1.

cheers,
Derick

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tyson andre

6 years ago

tyson andre

6 years ago

Hi internals,

https://wiki.php.net/rfc/opcache.no_cache has been updated.
Instead of opcache.no_cache=1, opcache.enable_cache=0 is now used to disable caching.

In the RFC, I wrote that opcache_get_status() now includes the following new booleans

- `optimizations_enabled`, which is true if any optimization passes will get run.
- `allow_cache`, which will be true if any form of opcode caching is enabled.
  Maybe `cache_opcodes` or `opcode_cache_enabled` would be a better name.

Any thoughts on whether opcache_get_status() should be changed at all here?
It's probably possible but inconvenient to determine what's being done with extension_loaded() and multiple calls to ini_get(),
and the intended meaning of existing flags such as `opcache_enabled` was never documented
in https://www.php.net/opcache_get_status

Any other thoughts on the RFC?

> > In my opinion, configuration names should never be "in the negative".
> > Instead of defaulting to opcache.no_cache=0, default to opcache.cache=1.
> 
> ... the setting isn't actually enabling cache, it's allowing cache (i.e. opposite of disabling),
> so making this "opcache.allow_cache" might be the best. I'll probably go with that.
> (similar to allow_url_fopen, allow_url_include)
> 
> ... `opcache.cache` could be confused with the caching strategy or the path to the cache,
> or being sufficient on its own to enable caching

Thanks,
- Tyson

Albert Casademont Filella

6 years ago

Hi tyson,

Thanks for your RFC. As ReactPHP users this is a very welcome change. Right
now we have to enable file_cache only for the optimizations, as there's no
real benefit of the full opcache in long-running CLI apps. Having this
setting would allow us to even stop using file_cache but get the opcache
optimizations. It would be even better if these optimizations moved into
PHP Core.

Thank you!

Albert

On Thu, May 21, 2020 at 4:07 PM tyson andre <tysonandre775@hotmail.com>
wrote:

tyson andre

6 years ago

Hi internals,

If there are no unexpected issues,
then voting will start on https://wiki.php.net/rfc/opcache.no_cache in 2 days, on May 30th.

Thanks,
- Tyson