Re: Oprofile Report

[dhara buch <dharabuchphd@gmail.com>]

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Actually, I am compiling a very simple c program test.c with

gcc -g test.c -o test

but it is not affecting output. Is there any way by which I can check
whether the binary image generates debug info or not?

On Fri, Mar 24, 2017 at 3:26 PM, Michael Petlan <mpetlan@redhat.com> wrote:

> Please read my previous message once more:
>
>       Hi, I think you need to rebuild the test with '-g' switch.
>       If the test binary does not have debuginfo, opreport cannot
>       resolve that.
>
> On Fri, 24 Mar 2017, dhara buch wrote:
>
>> Hi,
>> Yes, when I try to execute 'opreport --symbols --debug-info' command
>> after doing profiling for a .c file (let operf ./test),
>>
>> I am expecting 'test.c:line_no' in linear info field as you are getting
>> 'exact_counts.c:13' in the following:
>>
>> samples %        linenr info                 image name
>>  symbol name
>> 10       66.6667  (no location information)   no-vmlinux
>>  /no-vmlinux
>> 2        13.3333  exact_counts.c:13           exact_counts
>>  main
>> 1         6.6667  exact_counts.c:10           exact_counts
>>  f_65535x
>> 1         6.6667  exact_counts.c:9            exact_counts
>>  f_997x
>> 1         6.6667  (no location information)   ld-2.17.so
>>  _dl_fini
>> I tried to install debuginfo using
>> #debuginfo-install kernel command.
>>
>> But when I execute 'opreport --symbols --debug-info', I get only (no
>> location information)  in all of my samples.
>>
>> What may be the reason?
>>
>
> The reason is that OProfile cannot find debuginfo of your test app.
> Probably because it does not contain any ;-)
>
> Recompile your test application with the '-g' gcc switch.
>
>
> FURTHER INFO:
>
> If you are profiling an application installed from packages, you
> need to have the corresponding debuginfo package. For example,
> for profiling firefox, you need firefox-debuginfo (RHEL, Fedora,
> CentOS) or (probably) firefox-dbg packages (Ubuntu). It's also
> good to have the debuginfos of all the required libraries.
>
> On RHEL/CentOS/Fedora, you can install that easily by:
> debuginfo-install <your_package>
>
> Cheers,
> Michael
>
>
>
>> On Thu, Mar 23, 2017 at 8:08 PM, Michael Petlan <mpetlan@redhat.com>
>> wrote:
>>       On Thu, 23 Mar 2017, dhara buch wrote:
>>             Hello,
>>             I am doing profiling with command,
>>
>>             operf ./test --events=BR_INST_RETIRED
>>             where test.c is a simple c language file.
>>
>>             then, I am trying to collect information with command
>>
>>             opreport --symbols --debug-info
>>
>>             From the documents of Oprofile, I assume that the above
>> command lists profiling result as per the symbols i.e. I can get result
>> showing samples, linear info, image
>>             name and symbol name.
>>
>>             As per my command I expect my file name (test.c) to be in the
>> linear info and image name, but shows [no location information] in linear
>> info. The filename does not
>>             get listed in image
>>             name also.
>>
>>             What is lacking?
>>
>>
>>       Hi, I think you need to rebuild the test with '-g' switch.
>>       If the test binary does not have debuginfo, opreport cannot
>>       resolve that.
>>
>>       Me trying with debuginfo:
>>
>>       samples  %        linenr info                 image name
>>    symbol name
>>       10       66.6667  (no location information)   no-vmlinux
>>    /no-vmlinux
>>       2        13.3333  exact_counts.c:13           exact_counts
>>    main
>>       1         6.6667  exact_counts.c:10           exact_counts
>>    f_65535x
>>       1         6.6667  exact_counts.c:9            exact_counts
>>    f_997x
>>       1         6.6667  (no location information)   ld-2.17.so
>>      _dl_fini
>>
>>       And without:
>>
>>       samples  %        linenr info                 image name
>>    symbol name
>>       10       55.5556  (no location information)   no-vmlinux
>>    /no-vmlinux
>>       3        16.6667  (no location information)   exact_counts
>>    f_65535x
>>       2        11.1111  (no location information)   exact_counts
>>    main
>>       1         5.5556  (no location information)   ld-2.17.so
>>      _dl_add_to_slotinfo
>>       1         5.5556  (no location information)   ld-2.17.so
>>      _dl_next_tls_modid
>>       1         5.5556  (no location information)   ld-2.17.so
>>      _dl_relocate_object
>>
>>       Is this the problem you are asking about?
>>
>>
>>             I tried to set vmlinux with operf --vmlinux option also where
>> vmlinux file in in /usr/lib/debug/lib/4*/vmlinux, still the above commands
>> do not list test file
>>             entries.
>>
>>
>>       The "--vmlinux" option is there for enabling this for samples
>>       obtained in kernelspace.
>>
>>       By default (assuming you have no kernel debuginfo available),
>>       operf marks all the samples taken in kernel (e.g. your program
>>       called a syscall and the sample was taken when the syscall was
>>       being executed or you profile systemwide) as "no-vmlinux".
>>
>>       This is sufficient if you care about userspace only and not about
>>       the "time" spent in kernel.
>>
>>       If you care about kernelspace, you need the '--vmlinux' option
>>       with correct path specified.
>>
>>
>>             What is lacking?
>>
>>             Thank you,
>>
>>             Dhara buch
>>
>>
>>
>>       Has this helped?
>>
>>       Cheers,
>>       Michael
>>
>>
>>
>>

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