RFR: 8265836: OperatingSystemImpl.getCpuLoad() returns incorrect CPU load inside a container [v6]

[Hao Tang]

> OperatingSystemImpl.getCpuLoad() may return 1.0 in a container, even though the CPU load is obviously below 100%.
> 
> We created a 5-core container and run 4 "while (true)" loops in the container. OperatingSystemImpl.getCpuLoad() returned 1.0, which is incorrect (0.8 is correct).
> "systemLoad" in getCpuLoad() is exactly 4.0 before "systemLoad = Math.min(1.0, systemLoad);". The problem is caused by using the elapsed time (specified by "cpu.cfs_period_us") instead of the total CPU time (specified by "cpu.cfs_quota_us"). Therefore, it is more reasonable to divide cpu usage time by "quotaNanos" instead of "elapsedNanos".

Hao Tang has updated the pull request incrementally with two additional commits since the last revision:

 - Use historical-value-based formula for both cpu-quota-based and cpu-shares-based calculation
 - rename usageTicks and totalTicks

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3656/files
  - new: https://git.openjdk.java.net/jdk/pull/3656/files/c7abec03..eba3bc10

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3656&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3656&range=04-05

  Stats: 81 lines in 1 file changed: 32 ins; 39 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3656.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3656/head:pull/3656

PR: https://git.openjdk.java.net/jdk/pull/3656