I had perf working fine on my Cortex-A15 Chromebook running ARCH Linux ARM.
I updated pacman to get gcc-5.3, and it asked to update my kernel, so I did.
Now perf returns:
[cortex@alarm Speckle]$ perf stat uname -a
Linux alarm 3.8.11-3-ARCH #1 SMP Wed Jan 20 13:44:59 MST 2016 armv7l GNU/Linux
Performance counter stats for 'uname -a':
<not supported> task-clock
<not supported> context-switches
<not supported> cpu-migrations
<not supported> page-faults
<not supported> cycles
<not supported> stalled-cycles-frontend
<not supported> stalled-cycles-backend
<not supported> instructions
<not supported> branches
<not supported> branch-misses
0.002148765 seconds time elapsed
If I run perf list, it tells me it should be supporting these events:
[cortex@alarm Speckle]$ perf list
List of pre-defined events (to be used in -e):
branch-instructions OR branches [Hardware event]
branch-misses [Hardware event]
bus-cycles [Hardware event]
cache-misses [Hardware event]
cache-references [Hardware event]
cpu-cycles OR cycles [Hardware event]
instructions [Hardware event]
ref-cycles [Hardware event]
And checking my kernel configuration, it seems that perf should still be supported.
[cortex@alarm Speckle]$ zgrep PERF /proc/config.gz
CONFIG_CGROUP_PERF=y
CONFIG_HAVE_PERF_EVENTS=y
CONFIG_PERF_USE_VMALLOC=y
CONFIG_PERF_EVENTS=y
# CONFIG_DEBUG_PERF_USE_VMALLOC is not set
CONFIG_HW_PERF_EVENTS=y
# CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE is not set
CONFIG_CPU_FREQ_GOV_PERFORMANCE=y
# CONFIG_CLS_U32_PERF is not set
# CONFIG_DEVFREQ_GOV_PERFORMANCE is not set
If I try ocount/oprofile, it seems to work:
[cortex@alarm ~]$ ocount --events INST_RETIRED uname -a
Linux alarm 3.8.11-3-ARCH #1 SMP Wed Jan 20 13:44:59 MST 2016 armv7l GNU/Linux
Events were actively counted for 1598252 nanoseconds.
Event counts (actual) for /usr/bin/uname:
Event Count % time counted
INST_RETIRED 609,518 100.00
Looking at the pacman's log, it looks like this is where the kernel change occurred?
[2016-04-26 06:24] [ALPM] upgraded libtool (2.4.6-3 -> 2.4.6-4)
[2016-04-26 06:27] [ALPM] upgraded linux-firmware (20150904.6ebf5d5-1 -> 20160315.deb1d83-1)
[2016-04-26 06:27] [ALPM] upgraded linux-peach (3.8.11-2 -> 3.8.11-3)
[2016-04-26 06:27] [ALPM-SCRIPTLET] >>> Updating module dependencies. Please wait ...
[2016-04-26 06:27] [ALPM-SCRIPTLET] A new kernel version needs to be flashed onto /dev/sda1.
[2016-04-26 06:27] [ALPM-SCRIPTLET] Do you want to do this now? [y|N]
[2016-04-26 06:28] [ALPM-SCRIPTLET] 8752+0 records in
[2016-04-26 06:28] [ALPM-SCRIPTLET] 8752+0 records out
[2016-04-26 06:28] [ALPM-SCRIPTLET] 4481024 bytes (4.5 MB, 4.3 MiB) copied, 12.7236 s, 352 kB/s
What did I screw up and how do I get perf back?
The solution I found was to downgrade from perf 4.5-2 to perf 4.3-1.
cd /var/cache/pacman/pkg/
sudo pacman -U perf-4.3-1-armv7h.pkg.tar.xz
Running perf stat ls now returns the counters I expect.