RFR: JDK-8267371: Concurrent gtests take too long [v2]

[Thomas Stuefe]

> More than half of the total runtime of the gtests is currently used by just three tests:
> 
> - VirtualSpace.os_reserve_space_concurrent_vm
> - VirtualSpace.os_virtual_space_concurrent_vm
> - os_linux.reserve_memory_special_concurrent_vm
> 
> These tests do concurrent tests with 30 threads, with a timeout of 15 seconds each.
> 
> Since we run the gtests with several configurations (see hotspot/jtreg/gtests) these numbers multiply, which hurts especially when run as part of tier1. I think we can safely reduce the timeouts, still have good test coverage and recover some of the gtest runtime.
> 
> ---
> 
> The patch reduces the timeout to 5 seconds, which reduces the time for one gtest by 30 seconds from 80 seconds down to 50 seconds.

Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:

  5 threads 3 secs

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4110/files
  - new: https://git.openjdk.java.net/jdk/pull/4110/files/78e0c2c5..fd87020a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4110&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4110&range=00-01

  Stats: 8 lines in 3 files changed: 2 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4110.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4110/head:pull/4110

PR: https://git.openjdk.java.net/jdk/pull/4110