RFR: 8297292: java/nio/channels/FileChannel/FileExtensionAndMap.java is too slow [v2]

[Brian Burkhalter]

On Thu, 9 Feb 2023 16:44:15 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> Reduce the test’s disk space requirement by one third and the total number of files tested by half. With this change, the test was observed to still fail with a SIGBUS using JDK 11.0.15 on Linux 5.15.0-58. The test’s run time decreased by about two thirds: for one sample run from 29m56s to 10m13s in the CI on Linux-x64. A run with 50 repeats had no failures.
>
> Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8297292: Increment copyright year

`FileExtensionAndMap.java` was added by the change which resolved [JDK-8168628](https://bugs.openjdk.org/browse/JDK-8168628). That change was backed out of JDK 11 because it broke sparse files. The underlying issue was really `Unsafe::copy[Swap]Memory` not using memory guards which was tracked in [JDK-8191278](https://bugs.openjdk.org/browse/JDK-8191278). The fix for this latter issue added the test `test/hotspot/jtreg/runtime/Unsafe/InternalErrorTest.java` which is presumably sufficient to test for the underlying cause for which `FileExtensionAndMap.java` is also testing. Given this quasi duplication, it appears safe to simply remove `FileExtensionAndMap.java` altogether.

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PR: https://git.openjdk.org/jdk/pull/12479