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.