RFR: JDK-8150496,(zipfs) Fix performance issues in zip-fs

[Xueming Shen]

Hi,

Please help review the performance cleanup for zipfs

issue: https://bugs.openjdk.java.net/browse/JDK-8150496
webrev: http://cr.openjdk.java.net/~sherman/8150496/webrev

This is a cleanup update to improve the performance of most frequent
used access methods and the internal memory usage.

While there is definitely more places to investigate, it seems it is worth putting
the current version in with the performance improvement achieved.

Here are the result of the sample benchmark that measures the improvement.
http://cr.openjdk.java.net/~sherman/8150496/MyBenchmark.java

---------------------------------------new---------------------------------------
Benchmark                              Mode  Cnt     Score     Error  Units
MyBenchmark.ZFS_Exists                 avgt   25     4.380 ±   0.745  ms/op
MyBenchmark.ZFS_GetPath                avgt   25    11.722 ±   0.606  ms/op
MyBenchmark.ZFS_GetPathExists          avgt   25    21.031 ±   2.554  ms/op
MyBenchmark.ZFS_GetPathIsDirectory     avgt   25    26.823 ±   4.522  ms/op
MyBenchmark.ZFS_GetPathIsRegularFile   avgt   25    26.049 ±   3.441  ms/op
MyBenchmark.ZFS_GetPathNewInputStream  avgt   25    31.945 ±   3.330  ms/op
MyBenchmark.ZFS_GetPathToRealPath      avgt   25    21.375 ±   2.875  ms/op
MyBenchmark.ZFS_IsDirectory            avgt   25     9.309 ±   0.633  ms/op
MyBenchmark.ZFS_IsRegularFile          avgt   25     9.454 ±   0.928  ms/op
MyBenchmark.ZFS_Itr                    avgt   25    18.583 ±   0.841  ms/op
MyBenchmark.ZFS_Open                   avgt   25  1527.769 ± 221.997  ms/op
MyBenchmark.ZFS_ToRealPath             avgt   25     4.666 ±   0.584  ms/op
MyBenchmark.ZFS_newInputStream         avgt   25    14.864 ±   0.618  ms/op
----------------------------------------old---------------------------------------
Benchmark                              Mode  Cnt     Score     Error  Units
MyBenchmark.ZFS_Exists                 avgt   25    10.229 ±   1.236  ms/op
MyBenchmark.ZFS_GetPath                avgt   25    12.964 ±   2.739  ms/op
MyBenchmark.ZFS_GetPathExists          avgt   25    28.095 ±   3.595  ms/op
MyBenchmark.ZFS_GetPathIsDirectory     avgt   25    28.566 ±   1.430  ms/op
MyBenchmark.ZFS_GetPathIsRegularFile   avgt   25    29.102 ±   3.308  ms/op
MyBenchmark.ZFS_GetPathNewInputStream  avgt   25   151.271 ±   3.311  ms/op
MyBenchmark.ZFS_GetPathToRealPath      avgt   25    42.717 ±   6.112  ms/op
MyBenchmark.ZFS_IsDirectory            avgt   25    10.884 ±   0.810  ms/op
MyBenchmark.ZFS_IsRegularFile          avgt   25    11.801 ±   1.053  ms/op
MyBenchmark.ZFS_Itr                    avgt   25    21.498 ±   1.165  ms/op
MyBenchmark.ZFS_Open                   avgt   25  1673.597 ± 190.083  ms/op
MyBenchmark.ZFS_ToRealPath             avgt   25    19.266 ±   0.886  ms/op
MyBenchmark.ZFS_newInputStream         avgt   25   125.307 ±   2.818  ms/op


Thanks,
Sherman