Re: [Xen-devel] Oprofile Report

[dhara buch <dharabuchphd@xxxxxxxxx>]

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@xxxxxxxxxx> 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@xxxxxxxxxx> 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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