From: Mark Barnett <mark.barnett@xxxxxxx>
This patch introduces the concept of an alternating sample rate to perf
core and provides the necessary basic changes in the tools to activate
that option.
Changes since v1:
- Rebased onto perf-tools-next, as per request from Ian Rogers.
- Removed unnecessary code that truncated period_left to 0 and restarted
the PMU.
- Renamed variables to use the shorter 'alt_period' instead of
'alterantive_period'.
- Added patch #5 that addresses an issue in the x86 and PowerPC drivers that
caused the opposite period to be reported in the sample record.