RFR: 7903450: JMH: Improve -prof perfnorm accuracy with robust estimations [v2]

[Aleksey Shipilev]

> If we measure the mostly-idle workload, like the sleep-wait:
>   while (target > System.nanoTime()) Thread.sleep(1000);
> 
> ...then the `-prof perfnorm` measurement would mostly contain the iteration prologs/epilogs, which take orders of magnitude more cycles than the sleep itself. This can be alleviated by using a more robust estimator in perfnorm. The estimator can filter out the "outliers" caused by infrastructural overhead.

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Fix minTime calculation

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Changes:
  - all: https://git.openjdk.org/jmh/pull/114/files
  - new: https://git.openjdk.org/jmh/pull/114/files/03679e96..b8885e6f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmh&pr=114&range=01
 - incr: https://webrevs.openjdk.org/?repo=jmh&pr=114&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jmh/pull/114.diff
  Fetch: git fetch https://git.openjdk.org/jmh.git pull/114/head:pull/114

PR: https://git.openjdk.org/jmh/pull/114