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
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