[Telemetry] Fix power monitor negative c-state residency percentages.

[Telemetry] Fix power monitor negative c-state residency percentages.

Due to the latency of running separate shell commands, the length of a test
could sometimes be largely incorrect with respect to the cpu idle sample
times, causing c-state residency percent of some states to be several
points below zero.

BUG=336561
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=289618

[dbasehore, 2014-07-31 18:18:44]

https://codereview.chromium.org/425133002/diff/1/tools/telemetry/telemetry/co...
File
tools/telemetry/telemetry/core/platform/power_monitor/sysfs_power_monitor.py
(right):

https://codereview.chromium.org/425133002/diff/1/tools/telemetry/telemetry/co...
tools/telemetry/telemetry/core/platform/power_monitor/sysfs_power_monitor.py:87:
'cat %s %s %s; date +%%s' % (os.path.join(cpu_state_path, 'name'),
My only nit is that we might want to run cat and date before we need the values
so the programs are cached. This isn't likely need on anything without a
spinning hard drive though, so it's entirely optional.

We might also use python's time or chromium's if it has some api for that.

[dbasehore, 2014-07-31 18:26:20]

lgtm

[tbroch1, 2014-07-31 20:13:24]

lgtm

[tmandel, 2014-08-08 21:41:24]

The CQ bit was checked by tmandel@chromium.org

[commit-bot: I haz the power, 2014-08-08 21:42:40]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tmandel@chromium.org/425133002/1

[commit-bot: I haz the power, 2014-08-08 21:42:42]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-08-08 21:42:43]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[dbasehore, 2014-08-13 01:01:22]

Could one of the chromium committers review this change?

[achuithb, 2014-08-13 01:25:20]

On 2014/08/13 01:01:22, dbasehore wrote:
> Could one of the chromium committers review this change?

rubberstamp lgtm.

[tmandel, 2014-08-13 16:51:30]

The CQ bit was checked by tmandel@chromium.org

[commit-bot: I haz the power, 2014-08-13 16:53:16]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tmandel@chromium.org/425133002/1

[tmandel, 2014-08-13 16:58:25]

The CQ bit was unchecked by tmandel@chromium.org

[tmandel, 2014-08-13 17:10:25]

The CQ bit was checked by tmandel@chromium.org

[commit-bot: I haz the power, 2014-08-13 17:13:10]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tmandel@chromium.org/425133002/20001

[commit-bot: I haz the power, 2014-08-13 23:18:16]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_aosp on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_aosp/bu...)
  android_dbg on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_dbg/bui...)
  mac_chromium_rel_swarming on tryserver.chromium.mac
(http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[commit-bot: I haz the power, 2014-08-14 05:22:55]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-08-14 05:22:57]

Try jobs failed on following builders:
  android_aosp on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_aosp/bu...)

[tmandel, 2014-08-14 16:57:07]

The CQ bit was checked by tmandel@chromium.org

[commit-bot: I haz the power, 2014-08-14 16:59:01]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tmandel@chromium.org/425133002/20001

[commit-bot: I haz the power, 2014-08-14 17:01:40]

Committed patchset #2 (20001) as 289618