[petsc-users] Cray perftools

[Jed Brown]

If you can share before/after output from -log_view, it would likely help localize.

Another unintrusive thing (if you're allowed to run Linux perf) is to

$ perf record --call-graph dwarf -F99 ./app
[... runs ...]
$ perf script | stackcollapse-perf | flamegraph > flame.svg

and open flame.svg in a browser (it's interactive). This uses the flamegraph tools (https://github.com/brendangregg/FlameGraph). You can direct `perf script` to a file and share that if you can't/won't install flamegraph. This doesn't require compiling any special way and yet helps understand where time is spent.

Adrian Croucher <a.croucher at auckland.ac.nz> writes:

> hi,
>
> We have our PETSc-based code compiled on a Cray XC-50 machine, and it 
> has just recently started running about 2.5 times slower on there. 
> Neither the code nor PETSc has been recompiled lately.
>
> Turning the PETSc logging on, it appears to be spending more time on I/O 
> than it used to.
>
> The cluster admins have suggested we rebuild with the Cray "perftools" 
> module loaded to get profiling info. It's a slight hassle to rebuild 
> everything, so I wondered, would this actually tell us anything that we 
> don't already know from the PETSc logs?
>
> - Adrian
>
> -- 
> Dr Adrian Croucher
> Senior Research Fellow
> Department of Engineering Science
> University of Auckland, New Zealand
> email: a.croucher at auckland.ac.nz
> tel: +64 (0)9 923 4611