topic Resources about Intel® Transactional Synchronization Extensions (Intel TSX) in Intel® Moderncode for Parallel Architectures

Resources about Intel® Transactional Synchronization Extensions (Intel TSX)

Roman_D_Intel — Fri, 07 Jun 2013 13:56:58 GMT

Hi,

you might find this collection of technical material about Intel TSX instructions useful: http://www.intel.com/software/tsx

Best regards,

Roman

Thank you, Roman! Do you know

Andrey_Vladimirov — Fri, 07 Jun 2013 18:14:55 GMT

Thank you, Roman! Do you know if TSX will be integrated with OpenMP?

Andrey,

Roman_D_Intel — Fri, 07 Jun 2013 19:08:56 GMT

Andrey,

you are welcome. I would ask OpenMP guys.

Thanks,

Roman

As "an OpenMP guy", I'll

James_C_Intel2 — Mon, 10 Jun 2013 11:18:45 GMT

As "an OpenMP guy", I'll chime in.

We are intending to have support in the next compiler release for a way to request that omp_lock_t should use an adaptive TSX lock built on RTM.

We don't think it's a good idea to change the default implementation of omp_lock_t to make it speculative, because that can potentially slow code down significantly.

p.s. If you're interested in TSX you should read chapter 12 of the new tuning guide at https://www-ssl.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-optimization-manual.pdf

James,

jimdempseyatthecove — Mon, 10 Jun 2013 12:03:35 GMT

James,

I agree. The compiler may not know in advance if the lock is protecting an I/O operation or protecting a small critical section (using omp_lock_t). In the case of the I/O operation you likely would not want to use TSX/RTM. On the otherhand, in the case of a small critical section (using omp_lock_t) you would like to take advantage of TSX/RTM. Perhaps an alternalte omp runtime library call would suffice (you could write your own wrapper now).

The other place to recommend use of TSX or RTM is in !$OMP ATOMIC.

The !$OMP CRITICAL may be harder to please all with one policy. When the critical section is long lasting you may want the other threads to suspend. When it is short duration, then you might prefer to use TSX/RTM. Note, for short duration critical sections the user could use:

!$ CALL LOOPING_XBEGIN()
... code here ...
!$ CALL _XEND

Where LOOPING_XBEGIN() is a shell subroutine that loops when _XBEGIN aborts.

Jim Dempsey