mirrors/jgit - jgit - source @ dussan.org

Shawn Pearce aa8d5ac26c Remove unnecessary inflate stride in DfsBlock OpenJDK 7 does not benefit from using an inflate stride on the input array. The implementation of java.util.zip.Inflater supplies the entire input byte[] to libz, with no regards for the bounds supplied. Slicing at 512 byte increments in DfsBlock no longer has any benefit. In OpenJDK 6 the native portion of Inflater used GetByteArrayRegion to obtain a copy of the input buffer for libz. In this use case supplying a small stride made sense, it avoided allocating space for and copying data past the end of the object's compressed stream. In OpenJDK 7 the native code uses GetPrimitiveArrayCritical, which tries to avoid copying by freezing Java garbage collection and accessing the byte[] contents in place. On OpenJDK 7 derived JVMs it is likely more efficient to supply the entire DfsBlock. Since OpenJDK 5 and 6 are deprecated and replaced by OpenJDK 7 it is reasonable to suggest any consumers running JGit with DFS support use an OpenJDK 7 derived JVM. However, JGit still targets local filesystem support on Java 5, so it is still not reasonble to apply this same simplification to the internal.storage.file package. See: JDK-6751338 (http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6751338) Change-Id: Ib248b6d383da5c8aa887d9c355a0df6f3e2247a5	10 years ago
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eclipse/jgit	Remove unnecessary inflate stride in DfsBlock	10 years ago

Shawn Pearce aa8d5ac26c Remove unnecessary inflate stride in DfsBlock

OpenJDK 7 does not benefit from using an inflate stride on the input
array. The implementation of java.util.zip.Inflater supplies the
entire input byte[] to libz, with no regards for the bounds supplied.
Slicing at 512 byte increments in DfsBlock no longer has any benefit.

In OpenJDK 6 the native portion of Inflater used GetByteArrayRegion
to obtain a copy of the input buffer for libz. In this use case
supplying a small stride made sense, it avoided allocating space
for and copying data past the end of the object's compressed stream.

In OpenJDK 7 the native code uses GetPrimitiveArrayCritical,
which tries to avoid copying by freezing Java garbage collection
and accessing the byte[] contents in place. On OpenJDK 7 derived
JVMs it is likely more efficient to supply the entire DfsBlock.

Since OpenJDK 5 and 6 are deprecated and replaced by OpenJDK 7
it is reasonable to suggest any consumers running JGit with DFS
support use an OpenJDK 7 derived JVM. However, JGit still targets
local filesystem support on Java 5, so it is still not reasonble to
apply this same simplification to the internal.storage.file package.

See: JDK-6751338 (http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6751338)
Change-Id: Ib248b6d383da5c8aa887d9c355a0df6f3e2247a5

10 years ago

eclipse/jgit

Remove unnecessary inflate stride in DfsBlock

10 years ago