Re: Re: Wrong Perf Backtraces

Hi,
It seems that my previous e-mail is not sent, properly. So, here is a 
link to the stackoverflow question:
https://stackoverflow.com/questions/60766026/wrong-perf-backtraces

The perf is for Ubuntu 18.04 with the following "uname -a" output:
Linux Ahmad-Laptop 5.0.0-37-generic #40~18.04.1-Ubuntu SMP Thu Nov 14 
12:06:39 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
I also used a compiled Linux-5.4.7 kernel and its corresponding Perf 
tool.

Regards.

On 2020-03-23 13:19, Jiri Olsa wrote:

> On Mon, Mar 23, 2020 at 07:48:26AM +0430, ahmadkhorrami wrote:
> 
>> Here is a link to the detailed question at Stackoverflow:
>> 
>> https://stackoverflow.com/questions/60766026/wrong-perf-backtraces
> 
> hi,
> what perf version are you running?
> 
> jirka
> 
> I can copy it here, if needed.
> 
> Thanks
> 
> On 2020-03-23 05:04, Steven Rostedt wrote:
> 
> On Mon, 23 Mar 2020 00:54:01 +0430
> ahmadkhorrami <[email protected]> wrote:
> 
> Hi,
> I used "Perf" to extract call graphs in an evince benchmark. The 
> command
> used is as follows:
> sudo perf record -d --call-graph dwarf -c 10000 e
> mem_load_uops_retired.l3_miss:uppp /opt/evince-3.28.4/bin/evince
> 
> I extracted the backtraces using "perf script" and found out that there
> are many corrupted backtrace instances. Some contained repeated 
> function
> calls, for example two consecutive gmallocn()s exactly at the same
> offsets. There are also some backtraces where the callers and callees 
> do
> not match.
> Could you show some examples of the backtraces you mention?
> 
> Note that that mappings are correct. In other words, each single line 
> of
> the reported backtraces is correct (i.e., addresses match with
> functions). But is seems that there are some function calls in the
> middle, which are missed by "Perf". Strangely, in all runs (and also
> with different sampling frequencies) the problem occurs exactly at the
> same place.
> 
> I am really confused and looking forward to any help. I can also send
> backtraces if needed.
> -- Steve