Re: [PATCH v2] perf: libdw support for powerpc [ping]

Arnaldo Carvalho de Melo
2017-06-21T01:06:41Z

Em Thu, Jun 15, 2017 at 01:16:32PM +0200, Mark Wielaard escreveu:
> On Thu, 2017-06-15 at 10:46 +0200, Milian Wolff wrote:
> > Just a quick question: Have you guys applied my recent patch:
> >
> > commit 5ea0416f51cc93436bbe497c62ab49fd9cb245b6
> > Author: Milian Wolff <milian.wolff@kdab.com>
> > Date: Thu Jun 1 23:00:21 2017 +0200
> >
> > perf report: Include partial stacks unwound with libdw
> >
> > So far the whole stack was thrown away when any error occurred before
> > the maximum stack depth was unwound. This is actually a very common
> > scenario though. The stacks that got unwound so far are still
> > interesting. This removes a large chunk of differences when comparing
> > perf script output for libunwind and libdw perf unwinding.
> >
> > If not, then this could explain the issue you are seeing.
>
> Thanks! No, I didn't have that patch (*) yet. It makes a huge
> difference. With that, Paolo's patch and the elfutils libdw powerpc64
> fallback unwinder patch, it looks like I get user stack traces for
> everything now on ppc64le.

Can I take that as a Tested-by: you?

- Arnaldo

> Cheers,
>
> Mark
>
> (*) It just this one-liner, but what a difference that makes:
>
> --- a/tools/perf/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw.c
> @@ -224,7 +224,7 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
>
> err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
>
> - if (err && !ui->max_stack)
> + if (err && ui->max_stack != max_stack)
> err = 0;
>
> /*