When backporting [JDK-8312127](https://bugs.openjdk.org/browse/JDK-8312127), I realized there are no targeted tests for FileDescriptor.sync that can be used to qualify the changes in that area.
Additionally, we use FD.sync for durability in Java databases, and we want to make sure at least some smoke tests are available in OpenJDK. It will show, among other things, that the recent change to `FileDescriptor.sync` does not affect the performance much, compared to the cost of the `fsync` itself. Benchmark Mode Cnt Score Error Units # Before JDK-8312127 FileDescriptorSync.sync avgt 15 351,688 ? 2,477 ns/op # After JDK-8312127 FileDescriptorSync.sync avgt 15 353,331 ? 2,116 ns/op The new regression test completes in <0.5s on my Mac. ------------- Commit messages: - Fix Changes: https://git.openjdk.org/jdk/pull/15231/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15231&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8314120 Stats: 155 lines in 2 files changed: 155 ins; 0 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/15231.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/15231/head:pull/15231 PR: https://git.openjdk.org/jdk/pull/15231
