TELEMETRY: Don't always fail test when forcing CPUs fails.

TELEMETRY: Don't always fail test when forcing CPUs fails.

When enabling CPU cores for high-perf mode, only warn the
user rather than failing. Only --profiler=perf needs to
fail, since it's results would be invalid (vs. just noisy).

Also, kernel_max returns the number of CPU's supported by
the kernel, but the device may have less cores in practice 
(eg. Moto X/Moto E have kernel_max = 4). This uses the cpu*
files to determine the actual number of cores on the device.

BUG=383566
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=279321

[epennerAtGoogle, 2014-06-23 23:17:13]

Ptal.

[tonyg, 2014-06-24 02:16:54]

lgtm

https://codereview.chromium.org/336943008/diff/20001/build/android/pylib/perf...
File build/android/pylib/perf/perf_control.py (right):

https://codereview.chromium.org/336943008/diff/20001/build/android/pylib/perf...
build/android/pylib/perf/perf_control.py:26: assert self._num_cpu_cores > 0
We should add an error message to this assert.

https://codereview.chromium.org/336943008/diff/20001/build/android/pylib/perf...
build/android/pylib/perf/perf_control.py:44: raise RuntimeError('Failed to force
CPUs online. Can you adb root?')
We have methods that do this in android_commands.py: IsRootEnabled() and
EnableAdbRoot(). Should we just try to run that for them if not root, or fail
hard if root?

[epennerAtGoogle, 2014-06-24 02:35:58]

https://codereview.chromium.org/336943008/diff/20001/build/android/pylib/perf...
File build/android/pylib/perf/perf_control.py (right):

https://codereview.chromium.org/336943008/diff/20001/build/android/pylib/perf...
build/android/pylib/perf/perf_control.py:26: assert self._num_cpu_cores > 0
On 2014/06/24 02:16:54, tonyg wrote:
> We should add an error message to this assert.

Done.

https://codereview.chromium.org/336943008/diff/20001/build/android/pylib/perf...
build/android/pylib/perf/perf_control.py:44: raise RuntimeError('Failed to force
CPUs online. Can you adb root?')
On 2014/06/24 02:16:54, tonyg wrote:
> We have methods that do this in android_commands.py: IsRootEnabled() and
> EnableAdbRoot(). Should we just try to run that for them if not root, or fail
> hard if root?

The current check catches other problems, however the message is not clear
indeed. I broke this into two cases. If the CPUs are not online, I first check
for root and give a clear error message about that. Then fall back on the more
ambiguous error.

[epenner, 2014-06-24 02:37:41]

The CQ bit was checked by epenner@chromium.org

[commit-bot: I haz the power, 2014-06-24 02:38:29]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/epenner@chromium.org/336943008/40001

[commit-bot: I haz the power, 2014-06-24 05:00:56]

Change committed as 279321