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Date: Mon, 18 Aug 2008 21:46:46 +0400
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To: Arnaud Le Blanc <arnaud.lb@gmail.com>
CC: PHP Development <internals@lists.php.net>, 
 Stanislav Malyshev <stas@zend.com>,
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Subject: Re: [PHP-DEV] [PATCH] ZTS as fast as non-ZTS
From: dmitry@zend.com (Dmitry Stogov)

Hi Arnaud,

The patch looks very interesting.
I think it may be committed to the HEAD in the nearest future.
I don't have time to look into all details in the moment.

Could you explain why --with-tsrm-full-__thread-tls doesn't work with 
dlopen() however --with-tsrm-__thread-tls does?

Did you test the patch with DSO extensions?

It would be interesting to try the same idea on Windows with VC.

Thanks. Dmitry.

Arnaud Le Blanc wrote:
> Hi,
> 
> Currently the way globals work forces to pass a thread-local-storage pointer 
> across function calls, which involves some overhead. Also, not all functions 
> get the pointer as argument and need to use TSRMLS_FETCH(), which is slow. For 
> instance emalloc() involves a TSRMLS_FETCH(). An other overhead is accessing 
> globals, using multiple pointers in different locations.
> 
> The following patch caches each global address in a native TLS variable so 
> that accessing a global is as simple as global_name->member. This removes the 
> requirement of passing the tls pointer across function calls, so that the two 
> major overheads of ZTS builds are avoided.
> 
> Globals can optionally be declared statically, which speeds up things a bit.
> 
> Results in bench.php:
> non-ZTS:						3.7s
> ZTS unpatched:					5.2s
> ZTS patched:					4.0s
> ZTS patched and static globals:	3.8s
> 
> The patch introduces two new macros: TSRMG_D() (declare) and TSRMG_DH() 
> (declare, for headers) to declare globals, instead of the current "ts_rsrc_id 
> foo_global_id". These macros declare the global id, plus the __thread pointer 
> to the global storage.
> 
> ts_allocate_id now takes one more callback function as argument to bind the 
> global pointer to its storage. This callback is declared in TSRMG_D[H]().
> 
> As all TSRMLS_* macros now does nothing, it is needed to call ts_resource(0) 
> explicitly at least one time in each thread to initialize its storage. A new 
> TSRMLS_INIT() macro as been added for this purpose.
> 
> All this is disabled by default. --with-tsrm-__thread-tls enables the features 
> of the patch, and --with-tsrm-full-__thread-tls enables static declaration of 
> globals.
> 
> It as been tested on Linux compiled with --disable-all in CLI and a bit in 
> Apache2 with the worker MPM. Known issues: 
> - Declaring globals statically (--with-tsrm-full-__thread-tls) causes troubles 
> to dlopen(), actually Apache wont load the module at runtime (it works with 
> just --with-tsrm-__thread-tls).
> - The patch assumes that all resources are ts_allocate_id()'ed before any 
> other thread calls ts_allocate_id or ts_resource_ex(), which is possibly not 
> the case.
> 
> The patch needs some tweaks and does not pretend to be included in any branch, 
> but I would like to have some comments on it.
> 
> The patch: http://arnaud.lb.s3.amazonaws.com/__thread-tls.patch
> 
> Regards,
> 
> Arnaud
> 
>