[Openmp-commits] TLS for POWER

[Samuel F Antao]

The corresponding clang patch has been posted for review in
http://reviews.llvm.org/D10753.

Thanks!
Samuel

2015-06-22 21:40 GMT-04:00 Hal Finkel <hfinkel at anl.gov>:

> [+Johnny, Andrey]
>
> Any objections to this direction?
>
>  -Hal
>
> ----- Original Message -----
> > From: "Hal Finkel" <hfinkel at anl.gov>
> > To: "Alexandre Eichenberger" <alexe at us.ibm.com>
> > Cc: openmp-commits at dcs-maillist2.engr.illinois.edu
> > Sent: Monday, June 22, 2015 8:38:28 PM
> > Subject: Re: [Openmp-commits] TLS for POWER
> >
> > Hi Alexandre,
> >
> > Thanks!
> >
> > Please also post the Clang patch for review on the cfe list.
> >
> >  -Hal
> >
> > ----- Original Message -----
> > > From: "Alexandre Eichenberger" <alexe at us.ibm.com>
> > > To: "Hal Finkel" <hfinkel at anl.gov>
> > > Cc: openmp-commits at dcs-maillist2.engr.illinois.edu
> > > Sent: Monday, June 22, 2015 4:17:22 PM
> > > Subject: Re: [Openmp-commits] TLS for POWER
> > >
> > > Hal, Brian
> > >
> > > below is the revised patch.  I defined a new macro
> > > KMP_THREADPRIVATE_TLS
> > > that is currently set only for PPC64, and other architectures/OS
> > > can
> > > be
> > > added in that macro definition.
> > >
> > > I added comments when defining functions, as requested.
> > >
> > > I could not add "static" for the kmp_threadprivate.c function as it
> > > is
> > > defined there, but used in kmp_runtime.c
> > >
> > > Let me know of any additional suggestion you or fellow reviewers
> > > may
> > > have
> > >
> > > Alexandre
> > >
> > > (See attached file: threadprivate-patch2)
> > >
> > >
> > >
> > > From:       Hal Finkel <hfinkel at anl.gov>
> > > To: Alexandre Eichenberger/Watson/IBM at IBMUS
> > > Cc: <openmp-commits at dcs-maillist2.engr.illinois.edu>
> > > Date:       06/18/2015 12:50 PM
> > > Subject:    Re: [Openmp-commits] TLS for POWER
> > >
> > >
> > >
> > > Hi Alexandre,
> > >
> > > First, thanks for working on this! I think that we should
> > > definitely
> > > enable
> > > this mode of supporting thread locals if possible.
> > >
> > > As an organizational note, I think it would be better to add a new
> > > feature
> > > macro for using TLS in this way (currently enabled only for PPC64).
> > > As you
> > > point out, other architectures will likely also want to do this,
> > > and
> > > we
> > > should make this straightforward.
> > >
> > > +#if KMP_ARCH_PPC64
> > > +void kmpc_threadprivate_call_unprocessed_constructors();
> > > +#endif
> > >
> > > This function could be static, right?
> > >
> > > +       list. This is because each thread maintain a private
> > > variable
> > >
> > > maintain -> maintains
> > >
> > > +void
> > > +kmpc_threadprivate_call_unprocessed_constructors()
> > >
> > > I don't like that the comment explaining what this does is embedded
> > > in some
> > > other function (above). Please at least comment on where the
> > > comment
> > > is
> > > explaining what this does.
> > >
> > > +        // one or more register occured since the last parallel
> > > loop
> > >
> > > register -> registrations
> > >
> > >  -Hal
> > >
> > > ----- Original Message -----
> > > > From: "Alexandre Eichenberger" <alexe at us.ibm.com>
> > > > To: openmp-commits at dcs-maillist2.engr.illinois.edu
> > > > Sent: Friday, June 12, 2015 5:51:27 PM
> > > > Subject: [Openmp-commits] 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: tls_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
> > >
> > >
> > >
> >
> > --
> > 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
> >
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
> _______________________________________________
> Openmp-commits mailing list
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>
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