Hi Nikita,
On 2/13/19 12:02 PM, Nikita Popov wrote: > On Wed, Feb 13, 2019 at 9:26 AM Dmitry Stogov <dmi...@zend.com > <mailto:dmi...@zend.com>> wrote: > > Hi, > > > After JIT+ZTS related discussion with Joe and Bob, and some related > analyzes. > > I came to more or less formed design idea and described it at > https://wiki.php.net/zts-improvement > > This is not an RFC and I'm not sure, if I like to implement TSRM > changes myself now. > > > Comments are welcome. > > > Hi Dmitry, > > Thanks for looking into this issue. As a possible alternative I would > like to suggest the use of ZEND_TLS (__thread) for the EG/CG/BG etc > globals on Linux (on Windows this is not possible due to DLL linkage > restrictions). I played with __thread long time ago (may be 10 years), and that time it didn't work as expected. I can't remember the exact problems. May be it made troubles when used in DSO PHP build with DSO extensions, may be the size of "__thread" segment was limited, may be both. > __thread generates very good code (single load over %fs > segment with constant address) if the global is defined and used in an > executable. I suppose 2 loads: movq executor_globals@gottpoff(%rip), %rax movq %fs:field_offset(%rax), %rax > I'm not sure what kind of code it generates when TLS is > declared in an executable and used in a shared object, but as direct > access from extensions to the engine globals shouldn't be common, it's > probably okay even if it uses __tls_get_addr. The main problem with "__thread" might be portability. I especially thought about keeping TSRM layer with the same API, to avoid portability issues, but if "__thread" works fine, we definitely should use it. On the other hand, I'm not sure, who uses ZTS build today and if they need performance. Thanks. Dmitry. > > Nikita -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
