[Openmp-commits] Switch to TLS for POWER

[Churbanov, Andrey]

The library part of changes LGTM
(I mean threadprivate-path2).

Sorry for the late response, we still have some issues in the library related 
to the C++ thread_local, to be investigated further.

- Andrey

> -----Original Message-----
> From: openmp-commits-bounces at cs.uiuc.edu [mailto:openmp-commits-
> bounces at cs.uiuc.edu] On Behalf Of Hal Finkel
> Sent: Friday, July 03, 2015 1:53 AM
> To: Alexandre Eichenberger
> Cc: openmp-commits at dcs-maillist2.engr.illinois.edu
> Subject: Re: [Openmp-commits] Switch to TLS for POWER
> 
> Alexandre,
> 
> This needs to be committed at the same time as the Clang patch to keep
> everything working, correct?
> 
>  -Hal
> 
> ----- Original Message -----
> > From: "Alexandre Eichenberger" <alexe at us.ibm.com>
> > To: openmp-commits at dcs-maillist2.engr.illinois.edu
> > Sent: Thursday, June 4, 2015 7:40:46 AM
> > Subject: [Openmp-commits] Switch to TLS for POWER
> >
> >
> > I would like to request switching the threadprivate scheme to TLS
> > (Thread Level Storage) for POWER before we get legacy code out there.
> > Individual
> > measurements has shown TLS to have about 10x lower overhead (number
> > may change depending to the TLS scheme). TLS is also used by other
> > compilers (e.g. XL) and thus provide better interoperability.
> >
> > Approach is relatively simple: compiler still generate a call to
> > register the constructors and the destructors, but the functions
> > calling the constructor/destructors have been changed a bit so that
> > the compiler call the constructor on the TLS version of the object
> > (not the global one, as it currently is in KMP). Then, prior to
> > starting a parallel function, the workers check if there are no new
> > constructors/destructors that have been registered; if there are, they
> > will call the constructors prior to starting the parallel region.
> > Destructors are called when killing a worker thread.
> >
> > KMP code change have been done (exclusively under #def for power
> > architecture), LLVM changes have been done, code has been tested.
> > Commit
> > will need to be coordinated with the LLVM changes, which must go at
> > the same time.
> >
> > If there is interest, and no code legacy issue, this patch could also
> > be applied for other architectures that have TLS support.
> >
> > Alexandre
> >
> > (See attached file: june3-threadprivate-patch)
> > _______________________________________________
> > Openmp-commits mailing list
> > Openmp-commits at dcs-maillist2.engr.illinois.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/openmp-commits
> >
> 
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
> _______________________________________________
> Openmp-commits mailing list
> Openmp-commits at dcs-maillist2.engr.illinois.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/openmp-commits

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