RFR: 8259947: (fs) Optimize UnixPath.encode implementation [v4]

[Aleksey Shipilev]

On Wed, 20 Jan 2021 15:08:22 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> This patch improves `UnixPath.encode` by reusing `JLA.getBytesNoRepl` (which has fast-paths for common encoding) and avoiding a `toCharArray` call on the input by refactoring the `normalizeNativePath` code to operate on `String`. This might have a cost on files on Mac that need additional native normalization.
>> 
>> This removes another `ThreadLocal` and a source of `SoftReference`s. Together with the UTF-8 fast-path my UTF-8 encoded file system see substantial speed-ups in a trivial `new File(str).toPath()` microbenchmark.
>
> Claes Redestad has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:
> 
>  - Merge branch 'master' into unix_encode
>  - Move FileOpen.ToPath micros into top class
>  - Move JLA to top, add imports
>  - Fold ToPath into FileOpen, add root benchmarks to keep mix comparable
>  - Add micro. To properly examine cost of toPath() needs a new File due caching - use FileOpen as a baseline
>  - Optimize UnixPath.encode

Marked as reviewed by shade (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/2135