[Openmp-dev] Enabling OMPT by default

Tue Dec 19 10:52:10 PST 2017

Am 2017-12-19 15:15, schrieb Paul Osmialowski:
> Nah, it blocks forever on nested_lwt.c when I started it on 96-cores
> ARMv8.1 machine.

Can you get us a stack trace? I think we don't have access to an ARM 
machine to test ourselves but we might be able to guess based on the 
implementation.

> BTW, the missing part of callbacks.h for tests I added like this:
> 
> diff --git a/runtime/test/ompt/callback.h 
> b/runtime/test/ompt/callback.h
> index 8481fb4..9a560aa 100755
> --- a/runtime/test/ompt/callback.h
> +++ b/runtime/test/ompt/callback.h
> @@ -105,6 +105,11 @@ ompt_label_##id:
>  #define print_possible_return_addresses(addr) \
>    printf("%" PRIu64 ": current_address=%p\n", 
> ompt_get_thread_data()->value, \
>           ((char *)addr) - 8)
> +#elif KMP_ARCH_AARCH64
> +// On AArch64 the NOP instruction is 4 bytes long.
> +#define print_possible_return_addresses(addr) \
> +  printf("%" PRIu64 ": current_address=%p\n", 
> ompt_get_thread_data()->value, \
> +         ((char *)addr) - 4)
>  #else
>  #error Unsupported target architecture, cannot determine address 
> offset!
>  #endif

Interesting that we don't have a load instruction at all for AArch64. 
Sigh, that's why we have to customize it for every architecture...

> 
> On 18/12/2017 13:56, Jonas Hahnfeld via Openmp-dev wrote:
>> Does it pass the tests? I doubt that because it needs modifications as 
>> Joachim pointed out (had to do the same for PPC64).
>> 
>> Jonas
>> 
>> Am 2017-12-18 14:52, schrieb Pawel Osmialowski:
>>> Guys,
>>> 
>>> For more than a year I was always building libomp with
>>> -DLIBOMP_OMPT_SUPPORT=ON for our AArch64 machines and I'd happily see
>>> it enabled by default.
>>> 
>>> Cheers,
>>> Paul
>>> 
>>> 
>>> On Mon, 2017-12-18 at 14:23 +0100, Jonas Hahnfeld wrote:
>>>> Adding Paul, maybe he can help here. Though switching the default
>>>> for
>>>> x86/x86_64 and ppc64 doesn't mean it has to work on AArch64 for the
>>>> 6.0
>>>> release, it will just stay deactivated as for MIPS(64).
>>>> 
>>>> Jonas
>>>> 
>>>> Am 2017-12-18 13:02, schrieb Cownie, James H via Openmp-dev:
>>>> > The ARM folks should chip in. This should clearly be tested on
>>>> > AARCH64
>>>> > as well!
>>>> >
>>>> > -- Jim
>>>> >
>>>> > Jim Cownie <james.h.cownie at intel.com>
>>>> > SSG/DPD/TCAR (Technical Computing, Analyzers, and Runtimes)
>>>> > Tel: +44 117 9071438
>>>> >
>>>> > -----Original Message-----
>>>> > From: Openmp-dev [mailto:openmp-dev-bounces at lists.llvm.org] On
>>>> > Behalf
>>>> > Of Joachim Protze via Openmp-dev
>>>> > Sent: Monday, December 18, 2017 11:58 AM
>>>> > To: Openmp-dev <openmp-dev at lists.llvm.org>
>>>> > Subject: [Openmp-dev] Enabling OMPT by default
>>>> >
>>>> > Dear all,
>>>> >
>>>> > OpenMP 5.0 will introduce OMPT, the OpenMP tools interface. The
>>>> > current
>>>> > implementation in the LLVM/OpenMP runtime is at the level of
>>>> > OpenMP
>>>> > TR6,
>>>> > as published in November (with some known issues, were we have
>>>> > patches
>>>> > under review).
>>>> > Currently, this feature is deactivated by default
>>>> > (LIBOMP_OMPT_SUPPORT).
>>>> > According to overhead measurements performed by Intel and on some
>>>> > of
>>>> > our
>>>> > machines, this feature introduces a worst case runtime overhead of
>>>> > ~4%,
>>>> > but for most cases basically no overhead.
>>>> > As I understood, some of the build-bots run the tests when the
>>>> > feature
>>>> > is enabled. We locally test the changes continuously with different
>>>> > compiler versions (icc/gcc/clang), but only on x86_64 architecture.
>>>> > Further, this feature was tested on ppc64.
>>>> >
>>>> > How should we proceed to enable this feature by default, and get it
>>>> > tested on other architectures?
>>>> > For the 6.0 release, I would like to enable OMPT at least for the
>>>> > supported platforms x86/x86_64 and ppc64.
>>>> >
>>>> >
>>>> > We would also appreciate collaboration with vendors/users of other
>>>> > platforms, to ensure the code is running there.
>>>> >
>>>> > Typically, only the architecture specific offset needs to be added:
>>>> > https://github.com/llvm-mirror/openmp/blob/master/runtime/test/ompt
>>>> > /callback.h#L95
>>>> >
>>>> > Looking forward to your feedback,
>>>> >
>>>> > Joachim
>>>> > _______________________________________________
>>>> > Openmp-dev mailing list
>>>> > Openmp-dev at lists.llvm.org
>>>> > http://lists.llvm.org/cgi-bin/mailman/listinfo/openmp-dev
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