From: Milian Wolff <milian.wolff@kdab.com>
To: Travis Downs <travis.downs@gmail.com>
Cc: ak@linux.intel.com, jolsa@redhat.com,
linux-kernel@vger.kernel.org, jolsa@kernel.org,
namhyung@kernel.org, linux-perf-users@vger.kernel.org,
acme@kernel.org
Subject: Re: PEBS level 2/3 breaks dwarf unwinding! [WAS: Re: Broken dwarf unwinding - wrong stack pointer register value?]
Date: Thu, 15 Nov 2018 10:10:13 +0100 [thread overview]
Message-ID: <6310843.N4ooJGWzKY@agathebauer> (raw)
In-Reply-To: <CAOBGo4wPeobp90eqZF1apZxHUn-dnh6L3Rpt_=beR49o3XHY7g@mail.gmail.com>
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On Donnerstag, 15. November 2018 03:05:32 CET Travis Downs wrote:
> On Wed, Nov 14, 2018 at 8:20 AM Milian Wolff <milian.wolff@kdab.com> wrote:
> > 3) I suggest we always keep the first frame and sample IP from the user
> > regs, i.e. the accurate PEBS/IBS IP. Then we add the following frames
> > from unwinding the ustack with the iregs.
>
> Does this mean that the displayed unwind will sometimes be
> "impossible" to have actually be generated from a consistent execution
> of the user program?
Yes, that is exactly what I'm saying.
> For example, the top frame (from PEBS) and second frame (from iregs)
> may be inconsistent in that the latter function never calls the first.
> At this point it would be good to have an indication at the top frame
> is from a different source than the rest of the frames, lest the user
> pull is hair out trying to determine how function X seems to call
> function Y despite that not being the case in the source.
I agree. I personally like your suggested approach - only add an indication
when the IP differs so much that it points to a different function. What do
others say to this?
Cheers
--
Milian Wolff | milian.wolff@kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt, C++ and OpenGL Experts
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next prev parent reply other threads:[~2018-11-15 9:10 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-20 22:39 Broken dwarf unwinding - wrong stack pointer register value? Milian Wolff
2018-10-21 20:32 ` Milian Wolff
2018-10-22 10:35 ` Milian Wolff
2018-10-22 11:17 ` Milian Wolff
2018-10-22 13:58 ` Andi Kleen
2018-10-22 19:26 ` Milian Wolff
2018-10-23 4:03 ` Andi Kleen
2018-10-23 10:34 ` Milian Wolff
2018-10-24 14:48 ` Andi Kleen
2018-10-30 22:34 ` Milian Wolff
2018-11-01 22:08 ` PEBS level 2/3 breaks dwarf unwinding! [WAS: Re: Broken dwarf unwinding - wrong stack pointer register value?] Milian Wolff
2018-11-02 11:26 ` Jiri Olsa
2018-11-02 17:56 ` Milian Wolff
2018-11-05 20:51 ` Jiri Olsa
2018-11-05 22:54 ` Milian Wolff
2018-11-06 0:10 ` Andi Kleen
2018-11-06 8:39 ` Jiri Olsa
2018-11-06 17:26 ` Andi Kleen
2018-11-06 20:04 ` Milian Wolff
2018-11-06 20:24 ` Andi Kleen
2018-11-07 22:41 ` Milian Wolff
2018-11-08 12:41 ` Milian Wolff
2018-11-09 0:55 ` Andi Kleen
2018-11-09 0:54 ` Andi Kleen
2018-11-10 21:42 ` Travis Downs
2018-11-11 1:07 ` Andi Kleen
[not found] ` <CAOBGo4zirLiKX8VcROAE=kAD0+qkF0E-cBv9DtBiQr=_obDv5w@mail.gmail.com>
2018-11-11 2:54 ` Travis Downs
2018-11-12 3:26 ` Andi Kleen
2018-11-14 13:20 ` Milian Wolff
2018-11-15 2:05 ` Travis Downs
2018-11-15 9:10 ` Milian Wolff [this message]
2018-11-15 19:00 ` Andi Kleen
2018-11-15 2:15 ` Travis Downs
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