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

On Thu, 2017-06-15 at 10:46 +0200, Milian Wolff wrote:

Just a quick question: Have you guys applied my recent patch:
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commit 5ea0416f51cc93436bbe497c62ab49fd9cb245b6
Author: Milian Wolff [off-list ref]
Date:   Thu Jun 1 23:00:21 2017 +0200
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    perf report: Include partial stacks unwound with libdw
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    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.
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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.

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=

,
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        err =3D dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback=
, ui);
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-       if (err && !ui->max_stack)
+       if (err && ui->max_stack !=3D max_stack)
                err =3D 0;
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        /*