[Openmp-dev] initial clang-omp/openmp benchmarking

[Chandler Carruth]

On Thu, May 29, 2014 at 4:45 AM, Cownie, James H
<james.h.cownie at intel.com>wrote:

> I don’t really understand what problem you are complaining about.
>
> Your numbers show clang-omp as the fastest implementation in all directly
> comparable cases. That doesn’t seem like something we want to change!
>

I think the complaint is this: on Darwin, the scaling to 4 "processes" is
worse than on Linux.

However, the reason is stated already: Linux provides a *very* fast futex
implementation. Darwin either doesn't provide it or iomp doesn't use it.

If Darwin provides a fast futex interface, then iomp should use it. That's
a useful request. I don't know enough about Darwin to help investigate
whether the OS has a futex interface exposed to userland.

If Darwin doesn't provide a futex interface, there is literally nothing we
can do about that. You aren't going to match the scalability of a
kernel-supported futex with something in userspace.

Anyways, I do agree that micro-optimizing mutex performance for something
like openmp seems somewhat less important....
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/openmp-dev/attachments/20140529/f0b6fcb0/attachment.html>