Arnaud Le Blanc wrote:
Hi,
On Tuesday 19 August 2008 09:22:46 Dmitry Stogov wrote:
Hi Arnaud,
Arnaud Le Blanc wrote:
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.
I don't see a big difference between --with-tsrm-full-__thread-tls and
--with-tsrm-__thread-tls from TLS point of view (may be I miss it), so I
don't understand why one works and the other doesn't.
Badly both was not expected to work with dlopen() :(
http://marc.info/?l=php-internals&m=121912220705964&w=2
It works when using an other TLS model (which requires PIC).
This model is less efficient but it still improves performance. PIC-patched is
faster than non-PIC-unpatched, and the improvement is even greater against
PIC-unpatched.
This is the thing I was afraid.
The patch looks more difficult for me than it should. I would prefer to
have only --with-tsrm-full-__thread-tls, if it works, as the patch would
be simple and PHP faster.
Another simple solution, which you probably already tested, is to use
only global __thread-ed tsrm_ls (and don't pass/fetch it), however,
access thread-globals in the same way:
((*type)tsrm_ls[global_module_id])->global_fileld
Yes, I tested and it given 4.7s on bench.php (vs 3.8s with the current patch).
Does this model have the same issues with dlopen()?
(We have only one __thread-ed variable).
Thanks. Dmitry.
Anyway you did a great job. I would like to see this idea implemented in
HEAD. It is little bit late for 5.3 :(
Thanks. Dmitry.
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
Regards,
Arnaud
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