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Date: Wed, 24 Jul 2024 18:54:09 +0700
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Subject: Re: [PHP-DEV] tsrm question
To: Rob Landers <rob@bottled.codes>
Cc: internals@lists.php.net
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From: pierre.php@gmail.com (Pierre Joye)

Hi Rob,


On Wed, Jul 24, 2024 at 3:17=E2=80=AFPM Rob Landers <rob@bottled.codes> wro=
te:
>
> Hello internals,
>
> Last night I went down a rabbit hole with Frankenphp: https://github.com/=
dunglas/frankenphp/pull/933
>
> It isn't 100% clear to me what values `ts_resource(id)` holds and if it n=
eeds to be freed/allocated per request or per thread. The performance impac=
t is huge to reallocate on every request (mostly due to the global mutex du=
ring allocation). Is anyone familiar with this and could help reviewing the=
 changes there?

I suppose you already looked, but if not, maybe it gives you some direction=
(s).

The key part is kind of documented here:

https://github.com/php/php-src/blob/8e93eb2e79cea5fcca6769b46a429de042660da=
9/TSRM/TSRM.c#L417

tsrm knows nothing about requests but only threads.Its jobs are about
threads data.

A good start (surely already looked) are apache and litespeed (or
embed) for php8, however besides the API names change, the behavior or
goals of each ts_ or tsrm_ functions remain the same as what we had
with 5.x. One with a very similar modus operandi than Franken was
ISAPI for IIS. Mind the names changes, dapt to php8's new names (and
some behaviors) but the basics and core flows have been kept.

If you know (~) how many threads franken is going to need, tsrm allows
you to preallocate the rsc slots using tsrm_startup_ex. It uses
tsrm_startup, a more powerful version, which lets franken define how
many rsc per thread will be preallocated. I suppose that could help a
bit performance wise:

https://github.com/php/php-src/blob/8e93eb2e79cea5fcca6769b46a429de042660da=
9/main/main.c#L2716C13-L2716C25

As per the last question, about when to free them:
tsrm_shutdown (franken shutdown) will free all rsc

When a thread is detached (franken kills it for example),
ts_free_thread needs to be called to kill its rsc. They will be freed
anyway too but good to be clean.

The tsrm resource management will also automatically purge orphan rsrc
(f.e. when a thread dies unexpectedly and ts_free_thread could not be
called).

Long story short, the TSRM API is very flexible, how and when you
alloc/free rsrc is basically up to you. It is possible to keep some
around in the root thread (and be used in other threads, given the
root thread id is known (can be 0 or else depending how franken
managed them.

I hope it helps and did not say too many outdated/wrong explanations :).

Btw, Welting rewrote that part with Dmitry back then to fix long
standing issues (and drop TSRM_LS/DC/CC uses), not sure if he is still
around but he may help.

Best,
--
Pierre

@pierrejoye | http://www.libgd.org