hw perfevents on the pandabaord

[Ken Werner]

The 2.6.38-1001-linaro-omap kernel reports "unable to reserve pmu" when attempting to access hw counters using perf:
<snip>
  $ uname -a
  Linux panda 2.6.38-1001-linaro-omap #2-Ubuntu SMP Mon Mar 21 21:40:07 UTC 2011 armv7l armv7l armv7l GNU/Linux

  $ sudo su -c "echo -1 > /proc/sys/kernel/perf_event_paranoid" && cat /proc/sys/kernel/perf_event_paranoid
  -1

  $ sudo ./perf stat -e r63 -- sleep 1
  No permission to collect stats.
  Consider tweaking /proc/sys/kernel/perf_event_paranoid.

  $ dmesg | tail -1
  [10985.304809] hw perfevents: unable to reserve pmu

  $ sudo su -c "strace -e trace=perf_event_open ./perf stat -e r63 -- sleep 1"
  perf_event_open(0x1ed338, 0x114c, 0xffffffff, 0xffffffff, 0) = -1 ENODEV (No such device)
</snip>

The perf_event_open syscall returns ENODEV but the kernel config looks sane to me:
<snip>
  $ grep -i perf_ /boot/config-2.6.38-1001-linaro-omap
  # CONFIG_DEBUG_PERF_USE_VMALLOC is not set
  CONFIG_HAVE_PERF_EVENTS=y
  CONFIG_HW_PERF_EVENTS=y
  CONFIG_PERF_COUNTERS=y
  CONFIG_PERF_EVENTS=y
  CONFIG_PERF_USE_VMALLOC=y
</snip>

[Sachin Gupta (sachin-gupta)]

We need resolution for this bug as we need to validate system metics app on panda

[warmcat (andy-warmcat)]

Is this still broken on 3.0 kernel?

[Fathi Boudra (fboudra)]

Andy, see https://bugs.launchpad.net/bugs/843628

[Tom Gall (tom-gall)]

Trying this out with current release.

root@neso:~# perf stat -e r63 -- sleep 1
perf_3.1.1-15 not found
You may need to install linux-tools-3.1.1-15

I've looked for that version of linux-tools, it isn't in the archive and I don't see it in overlay or tools PPAs. Somebody outside of the MMWG needs to take ownership of it.

[Chase Qi (chase-qi)]

Migrated to bugzilla: https://bugs.linaro.org/show_bug.cgi?id=567