Re: OpenACC 2.5 Profiling Interface

[Jakub Jelinek <jakub@redhat.com>]

On Sun, Nov 11, 2018 at 10:31:42PM -0600, Thomas Schwinge wrote:
> On Tue, 28 Feb 2017 18:43:36 +0100, I wrote:
> > The 2.5 versions of the OpenACC standard added a new chapter "Profiling
> > Interface".
> 
> I'd like to get that into trunk.  It's not yet complete (that is, doesn't
> provide all the information specified), but it's very useful already, and
> the missing pieces can later be added incrementally.
> 
> Jakub, would you please especially review the non-OpenACC-specific
> changes here, including the libgomp ABI changes?
> 
> (Note that this patch doesn't apply on top of trunk.  I extracted it out
> of openacc-gcc-8-branch, plus additional changes, and it depends on a
> number of other pending patches.  Due to the many regions of code
> touched, there are a lot of "textual" conflicts when porting it to
> current trunk, but the "structure" will be the same.)

Seems rather expensive to me, especially with the dependence on
libbacktrace and the unconditional initialization of the profiling from the
library constructor.  Could e.g. libbacktrace or some libgomp plugin that is
linked against libbacktrace be dlopened only when apps ask for this stuff?

OpenMP 5 has a profiling API too (OMPT), there the rough plan for when it
will be implemented is that libgomp as the library will implement only the
absolute required minimum and perhaps have a variant library that is a
replacement for libgomp if more detailed instrumentation is needed.

	Jakub