RFR: JDK-8145260: To bring j.u.z.ZipFile's native implementation to Java to remove the expensive jni cost and mmap crash risk [2]

[Xueming Shen]

Hi,

The changeset for JDK-8142508 had been backout because it triggers jtreg 
fails in -avm mode
with testng tests. Here is the updated version that fixes the problem. 
I'm using a different issue
to trace this update change.

issue: https://bugs.openjdk.java.net/browse/JDK-8145260
webrev: http://cr.openjdk.java.net/~sherman/8145260/webrev/
diff: http://cr.openjdk.java.net/~sherman/8145260/diff  (diff to the 
latest 8142508 version)

The root cause/direct trigger that causes the jtreg failure is the 
overlook in the new implementation.
The flag "locsig" was implemented as

  this.locsig = (LOCSIG(buf) != LOCSIG);

while it really should be

  this.locsig = (LOCSIG(buf) == LOCSIG);

This is the flag that sun.misc.URLClassPath uses to check if a jar file 
stars with the correct
LOC (throws away if not) in certain circumstance (security manager + 
!disable_jar_checking).

This has been fixed in the new webrev, and I also renamed the field to 
be more straightforward
(locsig -> startsWithLoc)

Other than that, there are two small updates

(1) wrap the zip file initialization code with a try{} block and close 
the raw file if any exception
(2) reorder of "len <=0" check in ZipFileInputStream.read()

All tests seem to pass now.

Thanks,
Sherman

On 11/11/15 12:22 PM, Xueming Shen wrote:
> Hi
>
> Please help review the changes for JDK-8142508
>
> Issue: https://bugs.openjdk.java.net/browse/JDK-8142508
> webrev: http://cr.openjdk.java.net/~sherman/8142508/webrev
>
> Mainly to address the issues in current j.u.z.ZipFile implementation 
> as listed
> below
>
> (1) The ZIP file format support code is in native C (shared with the 
> VM via
>      ZipFile.c -> zip_util.c). Any entry lookup, creation operation 
> requires multiple
>      round-trips of expensive jni calls.
>
> (2) The native C implementation which uses mmap to map in the central 
> directory
>      table appears to be a big risk of vm crash when the underlying 
> jar file gets
>      overwritten with new contents while it is still being used by 
> other ZipFile. The
>      crash reports keep coming in even after we have introduced in 
> system flag
>      to disable it (sun.zip.disableMemoryMapping).
>
> (3) The use of "filename + lastModified()" cache (zip_util.c) appears 
> to be broken
>      if the timestamp is in low resolution/precision 
> (File.getModified() for example,
>      might only have "second" ersolution on solaris/linux), and/or the 
> file is being
>      overwritten.
>
> The clean solution appears to bring the ZIP format support code 
> completely from
> native to Java to remove the jni invocation cost and the mmap risk. 
> Also to use
> the fileKey and lastModified from 
> java.nio.file.attribute.BasicFileAttributes to have
> better/correct cache matching.
>
> Benchmark:
>
> This simple jmh measurement suggests a big boost of the performance of
> ZipFile.getEntry()/entries()/getStream() which are basically entry 
> related
> accesses (the "open only" has some regression, which is expected as we
> switched from the mmap to simply read the cen table in into a byte[])
>
> http://cr.openjdk.java.net/~sherman/8142508/MyBenchmark.java
>
> # JDK9 base
>
> Benchmark                  Mode  Cnt    Score    Error  Units
> MyBenchmark.testEntries    avgt   50   13.671 ±  0.385  ms/op
> MyBenchmark.testGetEntry   avgt   50   17.414 ±  0.803  ms/op
> MyBenchmark.testGetStream  avgt   50   42.398 ± 10.136  ms/op
> MyBenchmark.testOpen       avgt   50    3.049 ±  0.094  ms/op
> MyBenchmark.testRead       avgt   50  215.179 ±  9.926  ms/op
> MyBenchmark.testReadAll    avgt   50  244.422 ± 19.375  ms/op
> -------------------------------------------------------------------------------------- 
>
> # JDK9 ZipFile without jni invocation
>
> Benchmark                  Mode  Cnt    Score    Error  Units
> MyBenchmark.testEntries    avgt   50    6.436 ±  0.422  ms/op
> MyBenchmark.testGetEntry   avgt   50   10.021 ±  0.699  ms/op
> MyBenchmark.testGetStream  avgt   50   38.713 ± 16.687  ms/op
> MyBenchmark.testOpen       avgt   50    3.288 ±  0.119  ms/op
> MyBenchmark.testRead       avgt   50  220.653 ±  8.529  ms/op
> MyBenchmark.testReadAll    avgt   50  249.798 ± 18.438  ms/op
> --------------------------------------------------------------------------------------- 
>
>
> Test:
> http://cr.openjdk.java.net/~sherman/8142508/webrev/test/java/util/zip/ZipFile/TestZipFile.java.html 
>
>
> Verified the new ZipFile runs as expected when the underlying jar/zip 
> file get
> deleted/overwritten when the zip still be used. The "old" ZipFile 
> fails to continue
> to work but no crash, and the "new" one works correctly on updated zip 
> file
> without problem (The test runs a little long, have not decided if it 
> should be
> checked in as unit test).
>
> -Sherman
>