From: Milian Wolff <milian.wolff@kdab.com>
To: ahmadkhorrami <ahmadkhorrami@ut.ac.ir>
Cc: Jiri Olsa <jolsa@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Linux-trace Users <linux-trace-users@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
linux-trace-users-owner@vger.kernel.org,
Jin Yao <yao.jin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>,
Andi Kleen <ak@linux.intel.com>
Subject: Re: Wrong Perf Backtraces
Date: Tue, 31 Mar 2020 17:29:17 +0200 [thread overview]
Message-ID: <7774721.NyiUUSuA9g@agathebauer> (raw)
In-Reply-To: <fe8e797932c0cb6d1b8db2ee9b991ed0@ut.ac.ir>
[-- Attachment #1: Type: text/plain, Size: 1260 bytes --]
On Dienstag, 31. März 2020 17:02:37 CEST ahmadkhorrami wrote:
> Hi Milian,
> Thanks for the detailed answer. Well, the bug you mentioned is bad news.
> Because I sample using uppp. Perhaps this leads to these weird traces.
Please read the full thread from here on:
https://lkml.org/lkml/2018/11/2/86
But as I said - it should be easy to check if this is really the issue are
running into or not: Try to see if you see the problem when you sample without
`ppp`. If not, then you can be pretty sure it's this issue. If you still see
it, then it's something different.
> Is this a purely software bug?
I wouldn't call it that, personally. Rather, it's a limitation in the hardware
and software. We would need something completely different to "fix" this, i.e.
something like a deeper LBR. That's btw another alternative you could try:
`perf record --call-graph lbr` and live with the short call stacks. But at
least these should be correct (afaik). For me personally they are always far
too short and thus not practical to use in reality.
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
[-- Attachment #2: smime.p7s --]
[-- Type: application/pkcs7-signature, Size: 3826 bytes --]
next prev parent reply other threads:[~2020-03-31 15:29 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <157597d74ff17f781d9de7e7e3defd13@ut.ac.ir>
2020-03-22 20:24 ` Wrong Perf Backtraces ahmadkhorrami
2020-03-23 0:34 ` Steven Rostedt
[not found] ` <21b3df4080709f193d62b159887e2a83@ut.ac.ir>
2020-03-23 8:49 ` Jiri Olsa
2020-03-23 10:03 ` ahmadkhorrami
2020-03-25 15:18 ` ahmadkhorrami
2020-03-25 15:46 ` Jiri Olsa
2020-03-25 18:54 ` ahmadkhorrami
2020-03-25 18:58 ` Arnaldo Carvalho de Melo
2020-03-25 19:10 ` ahmadkhorrami
2020-03-25 19:28 ` Arnaldo Carvalho de Melo
2020-03-25 20:01 ` ahmadkhorrami
2020-03-25 20:39 ` Jiri Olsa
2020-03-25 21:02 ` Jiri Olsa
2020-03-25 21:09 ` Steven Rostedt
2020-03-25 21:37 ` ahmadkhorrami
2020-03-25 21:46 ` Jiri Olsa
2020-03-25 22:21 ` ahmadkhorrami
2020-03-25 23:09 ` ahmadkhorrami
2020-03-26 9:59 ` Jiri Olsa
2020-03-26 13:20 ` ahmadkhorrami
2020-03-26 15:39 ` Jiri Olsa
2020-03-26 18:19 ` ahmadkhorrami
2020-03-26 18:21 ` ahmadkhorrami
2020-03-27 9:20 ` Jiri Olsa
2020-03-27 10:59 ` ahmadkhorrami
2020-03-27 11:04 ` ahmadkhorrami
2020-03-27 12:10 ` Milian Wolff
2020-03-27 12:58 ` ahmadkhorrami
2020-03-27 13:25 ` Milian Wolff
2020-03-27 13:33 ` ahmadkhorrami
2020-03-27 18:43 ` ahmadkhorrami
2020-03-27 22:37 ` Jiri Olsa
2020-03-27 23:12 ` ahmadkhorrami
2020-03-28 23:34 ` Jiri Olsa
2020-03-29 0:43 ` ahmadkhorrami
2020-03-29 1:16 ` ahmadkhorrami
2020-03-29 11:19 ` Jiri Olsa
2020-03-29 11:52 ` ahmadkhorrami
2020-03-29 12:08 ` Jiri Olsa
2020-03-29 12:39 ` ahmadkhorrami
2020-03-29 13:50 ` Milian Wolff
2020-03-29 14:23 ` ahmadkhorrami
2020-03-29 19:20 ` Jiri Olsa
2020-03-30 6:09 ` Milian Wolff
2020-03-30 13:07 ` Jiri Olsa
2020-03-30 13:49 ` ahmadkhorrami
2020-03-30 19:05 ` ahmadkhorrami
2020-03-30 21:05 ` debuginfod-based dwarf downloading, was " Frank Ch. Eigler
2020-03-31 9:26 ` Jiri Olsa
2020-03-31 14:00 ` Frank Ch. Eigler
2020-03-31 4:43 ` ahmadkhorrami
2020-03-31 9:30 ` Jiri Olsa
2020-03-31 11:53 ` ahmadkhorrami
2020-03-31 12:43 ` ahmadkhorrami
2020-03-31 13:20 ` Jiri Olsa
2020-03-31 13:39 ` ahmadkhorrami
2020-03-31 14:44 ` Milian Wolff
2020-03-31 15:02 ` ahmadkhorrami
2020-03-31 15:05 ` ahmadkhorrami
2020-03-31 15:29 ` Milian Wolff [this message]
2020-03-31 16:10 ` Arnaldo Carvalho de Melo
2020-03-31 19:20 ` ahmadkhorrami
2020-03-31 19:17 ` ahmadkhorrami
2020-03-31 20:57 ` ahmadkhorrami
2020-04-04 1:01 ` ahmadkhorrami
2020-04-11 16:42 ` ahmadkhorrami
2020-04-11 21:04 ` ahmadkhorrami
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7774721.NyiUUSuA9g@agathebauer \
--to=milian.wolff@kdab.com \
--cc=acme@redhat.com \
--cc=ahmadkhorrami@ut.ac.ir \
--cc=ak@linux.intel.com \
--cc=jolsa@redhat.com \
--cc=linux-trace-users-owner@vger.kernel.org \
--cc=linux-trace-users@vger.kernel.org \
--cc=namhyung@kernel.org \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=yao.jin@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).