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To: Dmitry Stogov <dmitry@zend.com>
Date: Tue, 19 Aug 2008 01:16:04 +0200
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Cc: PHP Development <internals@lists.php.net>,
 Stanislav Malyshev <stas@zend.com>,
 Andi Gutmans <andi@zend.com>
References: <200808170419.11153.arnaud.lb@gmail.com> <48A9B586.6000409@zend.com>
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Message-ID: <200808190116.04713.arnaud.lb@gmail.com>
Subject: Re: [PHP-DEV] [PATCH] ZTS as fast as non-ZTS
From: arnaud.lb@gmail.com (Arnaud Le Blanc)

Hi,

On Monday 18 August 2008 19:46:46 Dmitry Stogov wrote:
> 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?

That's due to the way TLS works internally. Actually I need further reading on 
that.

> 
> Did you test the patch with DSO extensions?

I will, but I guess that will be behaves like another shared library 
dlopen()ed by Apache.

> 
> It would be interesting to try the same idea on Windows with VC.

I will try too.

> 
> 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
> > 
> > 
> 

Regards,

Arnaud