----- Original Message ----- From: "Stefan Strasser" <strasser@uni-bremen.de> To: <boost@lists.boost.org> Sent: Friday, January 08, 2010 7:37 PM Subject: [boost] [thread] thread_specific_ptr performance (was: Re: Boostlibrary submission (poll for interest))
Am Friday 08 January 2010 16:39:27 schrieb Rutger ter Borg:
1) Transactional semantics: wouldn't it be easier to steal semantics from locks in threads? E.g., for the synchronous interface case, wouldn't
map_type m_map; try { scoped_transaction trans( m_map ); .. .. do stuff with the map .. trans.commit(); } catch( transaction_error ) { }
be a easier than passing the transaction everywhere?
implementing this requires a call to thread_specific_ptr::get() on each operation to obtain the active transaction.
unfortunately thread_specific_ptr is implemented using pthread calls and a std::map lookup, so this consumes > 6% CPU in one of my test cases. and this is a real world test case with other expensive stuff, in cases that e.g. only read cached objects it's probably even worse.
is there any chance for a thread_specific_ptr implementation based on GCC __thread and MSVC __declspec(thread)?
__thread results in a simple read access using a thread-specific memory segment.
Hi, As Anthony has already state on other threads this seems to be not posible (the semantic is different). What about defining a macro BOOST_LOCAL_THREAD that do the needed portable issues? Have you make some measures with __thread and/or MSVC __declspec(thread)? BTW, Anthony has made some improvements to which thread_specific_ptr in 1.41. Which version are you using? Best, Vicente