Perf Tool Linux

2018-06-28 15:45:35

I am tring to use perf version 3.0.8 to profile my embedded system Linux kernel version 3.0.8 .

I cross-compiled tools/perf using zlib and elfutils.

In order to familiarize with this tool I am using a simple quicksort example compiled using -g option.

I run perf record -F 99 -g -- ./qsort (copied from the example) and then perf report --stdio to see my profile results.

This is a snapshot of the perf report -g --stdio output:

No kallsyms or vmlinux with build-id f41dfb5606beda1d75171db69f1e9466cb4868ba was found
[hi3518_dsu] with build id f41dfb5606beda1d75171db69f1e9466cb4868ba not found, continuing without symbols
No kallsyms or vmlinux with build-id a0f9a05faf6bcfb72282a03e048b47e8a8c0f2ec was found
[hi3518_tde] with build id a0f9a05faf6bcfb72282a03e048b47e8a8c0f2ec not found, continuing without symbols

# Events: 256  cpu-clock
    #
    # Overhead  Command      Shared Object                  Symbol
    # ........  .......  .................  ......................
    #
        96.88%    qsort  qsort              [.] partition
         0.78%    qsort  [kernel.kallsyms]  [k] __do_softirq
         0.39%    qsort  [kernel.kallsyms]  [k] __wake_up_sync_key
         0.39%    qsort  [kernel.kallsyms]  [k] get_page_from_freelist
         0.39%    qsort  [kernel.kallsyms]  [k] __memzero
         0.39%    qsort  [kernel.kallsyms]  [k] div_s64_rem
         0.39%    qsort  [hi3518_tde]       [k] 0x58
         0.39%    qsort  [hi3518_dsu]       [k] 0x8154

As you can see there is not call-trace at all. I am really interested to study in deep my system and without a call-trace these results are useless.

You might have some luck using the -fno-omit-frame-pointer flag while compiling the program you are trying to profile. I am also having issues making call graphs work with perf on an ARM embedded system.

I found a solution. Run perf --call-graph dwarf -- ./qsort Make sure you have compiled the program with dwarf debug symbols (-g, -ggdb, or -gdwarf flag). In addition, you might need to install debug symbols for any libraries you are using on your system. https://fedoraproject.org/wiki/StackTraces shows how to install debug symbol packages for Fedora.

If the perf command fails with --call-graph dwarf, you may need to compile perf with libunwind in addition to elfutils.

Probably my pref version is really old (or/and the kernel tool). I tried with another soc (with a newer kernel and perf tool) and the callstack works properly. However, even without this feature, I'm using this tool profitably.

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