07 Aug, 2015

1 commit


18 Sep, 2014

1 commit

  • Decoding an Intel PT trace of the kernel requires an accurate kernel
    object image. This is provided by making a copy of kcore. However the
    copy needs to be made under the same conditions as the original
    recording, and then it needs to be associated with the perf.data file.
    The perf-with-kcore script does that.

    The script also checks the permissions on the buildid cache and can be
    used to fix them. That is needed for distributions where root does not
    have a home directory and consequently writes to the same buildid cache
    as the user, resulting in cached files that the user does not have
    access to.

    Example:

    $ ./perf-with-kcore
    Usage: perf-with-kcore [ [ -- ]]
    can be record, script, report or inject
    or: perf-with-kcore fix_buildid_cache_permissions
    $ ./perf-with-kcore record pt_uname -e intel_pt// -- uname
    Recording
    Using /home/ahunter/bin/perf
    perf version 3.15.rc3.g4549ba
    /home/ahunter/bin/perf record -o pt_uname/perf.data -e intel_pt// -- uname
    Linux
    [ perf record: Woken up 3 times to write data ]
    [ perf record: Captured and wrote 0.023 MB pt_uname/perf.data ]
    Copying kcore
    [sudo] password for ahunter:
    Done
    $ tools/perf/perf-with-kcore.sh script pt_uname | head
    Using /home/ahunter/bin/perf
    perf version 3.15.rc3.g4549ba
    /home/ahunter/bin/perf script -i pt_uname/perf.data --kallsyms=pt_uname/kcore_dir/kallsyms
    swapper 0 [002] 161533.969666: sched:sched_switch: swapper/2:0 [120] R ==> perf:11316 [120]
    :11315 11315 [003] 161533.969704: sched:sched_switch: perf:11315 [120] S ==> swapper/3:0 [120]
    :11316 11316 [002] 161533.969783: sched:sched_switch: perf:11316 [120] R ==> migration/2:33 [0]
    :33 33 [002] 161533.969791: sched:sched_switch: migration/2:33 [0] S ==> swapper/2:0 [120]
    swapper 0 [003] 161533.969792: sched:sched_switch: swapper/3:0 [120] R ==> perf:11316 [120]
    :11316 11316 [003] 161533.970062: branches: 0 [unknown] ([unknown]) => ffffffff810532fa native_write_msr_safe ([kernel.kallsyms])
    :11316 11316 [003] 161533.970062: branches: ffffffff810532fd native_write_msr_safe ([kernel.kallsyms]) => ffffffff81035b31 pt_config_start ([kernel.kallsyms])

    Signed-off-by: Adrian Hunter
    Cc: David Ahern
    Cc: Frederic Weisbecker
    Cc: Jiri Olsa
    Cc: Namhyung Kim
    Cc: Paul Mackerras
    Cc: Peter Zijlstra
    Cc: Stephane Eranian
    Link: http://lkml.kernel.org/r/1406786474-9306-30-git-send-email-adrian.hunter@intel.com
    Signed-off-by: Arnaldo Carvalho de Melo

    Adrian Hunter