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Date: Mon, 18 Aug 2008 21:18:51 -0700
Message-ID: <698DE66518E7CA45812BD18E807866CE01E77474@us-ex1.zend.net>
In-Reply-To: <200808170419.11153.arnaud.lb@gmail.com>
Thread-Topic: [PHP-DEV] [PATCH] ZTS as fast as non-ZTS
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References: <200808170419.11153.arnaud.lb@gmail.com>
To: "Arnaud Le Blanc" <arnaud.lb@gmail.com>,
	"PHP Development" <internals@lists.php.net>
Subject: RE: [PHP-DEV] [PATCH] ZTS as fast as non-ZTS
From: andi@zend.com ("Andi Gutmans")

Hi Arnaud,

I remember that at the time we looked at thread local storage and there
were some real issues with it. I can't remember what as it was about 7+
years ago.
I will ask Zeev if he remembers and if not search my archives (don't
have years prior to 2007 indexed :'( ).

Andi




> -----Original Message-----
> From: Arnaud Le Blanc [mailto:arnaud.lb@gmail.com]
> Sent: Saturday, August 16, 2008 7:19 PM
> To: PHP Development
> Subject: [PHP-DEV] [PATCH] ZTS as fast as non-ZTS
>=20
> Hi,
>=20
> 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.
>=20
> 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.
>=20
> Globals can optionally be declared statically, which speeds up things
a bit.
>=20
> Results in bench.php:
> non-ZTS:						3.7s
> ZTS unpatched:					5.2s
> ZTS patched:					4.0s
> ZTS patched and static globals:	3.8s
>=20
> 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.
>=20
> 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]().
>=20
> 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.
>=20
> 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.
>=20
> 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.
>=20
> 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.
>=20
> The patch: http://arnaud.lb.s3.amazonaws.com/__thread-tls.patch
>=20
> Regards,
>=20
> Arnaud
>=20
>=20
> --
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