Fwd: RFR: JDK-8147460: Clean-up jrtfs implementation

[Xueming Shen]

[re-post, including jigsaw list]

Hi,

Please hep review the cleanup changes for jrtfs implementation.

issue: https://bugs.openjdk.java.net/browse/JDK-8147460
webrev: http://cr.openjdk.java.net/~sherman/8147460/webrev

Simple benchmark [1] has been run both on jimage and the "exploded modules"
directory, the numbers suggest we also get an encouraging performance boost
on most of the frequently invoked access methods.

[1] http://cr.openjdk.java.net/~sherman/8147460/MyBenchmark.java

Benchmark                      Mode  Cnt   Score   Error  Units
------------------------------------------------------------
[jimage/existing]
MyBenchmark.testExists         avgt   50  18.592 ± 1.213  ms/op
MyBenchmark.testIsDirectory    avgt   50  17.382 ± 1.178  ms/op
MyBenchmark.testIsRegularFile  avgt   50  18.576 ± 1.577  ms/op
MyBenchmark.testItr            avgt   50  58.414 ± 1.638  ms/op
MyBenchmark.testLookupPath     avgt   50  18.935 ± 1.093  ms/op
MyBenchmark.testLookupStr      avgt   50  38.597 ± 1.663  ms/op
MyBenchmark.testToRealPath     avgt   50  30.119 ± 1.196  ms/op

[jimage/new]
MyBenchmark.testExists         avgt   50  10.865 ± 1.125  ms/op
MyBenchmark.testIsDirectory    avgt   50  11.077 ± 1.101  ms/op
MyBenchmark.testIsRegularFile  avgt   50  10.967 ± 1.220  ms/op
MyBenchmark.testItr            avgt   50  49.249 ± 3.753  ms/op
MyBenchmark.testLookupPath     avgt   50  10.857 ± 1.071  ms/op
MyBenchmark.testLookupStr      avgt   50  34.367 ± 1.341  ms/op
MyBenchmark.testToRealPath     avgt   50  11.460 ± 1.081  ms/op

------------------------------------------------------------
[exploded dir/existing]
MyBenchmark.testExists         avgt   50   23.055 ± 1.707  ms/op
MyBenchmark.testIsDirectory    avgt   50   23.985 ± 1.593  ms/op
MyBenchmark.testIsRegularFile  avgt   50   24.200 ± 1.744  ms/op
MyBenchmark.testItr            avgt   50  210.002 ± 6.954  ms/op
MyBenchmark.testLookupPath     avgt   50   23.242 ± 1.799  ms/op
MyBenchmark.testLookupStr      avgt   50   43.026 ± 1.751  ms/op
MyBenchmark.testToRealPath     avgt   50   56.536 ± 1.679  ms/op

[exploded dir/new]
MyBenchmark.testExists         avgt   50  11.260 ± 1.209  ms/op
MyBenchmark.testIsDirectory    avgt   50  11.702 ± 1.069  ms/op
MyBenchmark.testIsRegularFile  avgt   50  12.284 ± 1.333  ms/op
MyBenchmark.testItr            avgt   50  49.342 ± 1.516  ms/op
MyBenchmark.testLookupPath     avgt   50  11.041 ± 1.051  ms/op
MyBenchmark.testLookupStr      avgt   50  35.850 ± 1.618  ms/op
MyBenchmark.testToRealPath     avgt   50  13.016 ± 1.339  ms/op

Thanks,
Sherman