Re: [GIT PULL 00/30] perf/core improvements and fixes

[Namhyung Kim <namhyung@kernel.org>]

On Mon, May 11, 2015 at 11:06:26AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Mon, May 11, 2015 at 02:09:39PM +0900, Namhyung Kim escreveu:
> > Hi Arnaldo,
> > 
> > I'm seeing a segfault on 'perf report' with a large data file after
> > applying thread refcount change - it happens regardless of the atomic
> > operation.
> 
> Any specific 'perf record' command line? Does it take a long time to
> reproduce? Any backtraces? I'll try to repro, its possible that we're
> doing one too many thread__put()...

It's a kernel build with '-j 20' and recorded data size is ~2.1GB.
It takes ~30 sec to reproduce.

  $ perf report -i threaded/kbuild7.data --header-only
  # ========
  # captured on: Thu Dec 18 12:06:35 2014
  # hostname : sejong
  # os release : 3.17.4-1-ARCH
  # perf version : 3.18.rc3.gcb4774b
  # arch : x86_64
  # nrcpus online : 12
  # nrcpus avail : 12
  # cpudesc : Intel(R) Core(TM) i7-3930K CPU @ 3.20GHz
  # cpuid : GenuineIntel,6,45,7
  # total memory : 24646828 kB
  # cmdline : /home/namhyung/project/linux/tools/perf/perf record -ag -o /home/namhyung/tmp/perf/threaded/kbuild7.data -- make -j20
  # event : name = cycles, , size = 104, { sample_period, sample_freq } = 4000, sample_type = IP|TID|TIME|CALLCHAIN|CPU|PERIOD, disabled = 1, inherit
  # HEADER_CPU_TOPOLOGY info available, use -I to display
  # HEADER_NUMA_TOPOLOGY info available, use -I to display
  # pmu mappings: cpu = 4, software = 1, power = 24, uncore_pcu = 13, tracepoint = 2, uncore_imc_0 = 15, uncore_imc_1 = 16, uncore_imc_2 = 17, uncore_
  # ========
  #


  $ perf data stat -i threaded/kbuild7.data

   Total event stats for 'threaded/kbuild7.data' file:
  
             TOTAL events:   25126492
              MMAP events:        114
              COMM events:     117957
              EXIT events:     240544
          THROTTLE events:         16
        UNTHROTTLE events:         16
              FORK events:     120488
            SAMPLE events:   23878219
             MMAP2 events:     745325
    FINISHED_ROUND events:      23813
  
   Sample event stats:
  
  20,579,564,471,104      cycles
          23,878,219      samples                   #   sampling ratio  99.745% (3989/4000)

       498.736917889 second time sampled


  $ perf report -i threaded/kbuild7.data
  perf: Segmentation fault
  -------- backtrace --------
  perf[0x51c7cb]
  /usr/lib/libc.so.6(+0x33540)[0x7f37eb37e540]
  /usr/lib/libc.so.6(+0x9029e)[0x7f37eb3db29e]
  perf[0x4dd9c8]
  perf(__hists__add_entry+0x188)[0x4e2258]
  perf[0x4e2580]
  perf(hist_entry_iter__add+0x9d)[0x4e2a7d]
  perf[0x437fda]
  perf[0x4c4c8e]
  perf[0x4c5176]
  perf[0x4c8bab]
  perf[0x4c53c2]
  perf[0x4c5f0c]
  perf(perf_session__process_events+0xb3)[0x4c6b23]
  perf(cmd_report+0x12a0)[0x439310]
  perf[0x483ec3]
  perf(main+0x60a)[0x42979a]
  /usr/lib/libc.so.6(__libc_start_main+0xf0)[0x7f37eb36b800]
  perf(_start+0x29)[0x4298b9]
  [0x0]

It seems like some memory area was corrupted..

Thanks,
Namhyung