Hi,
please review this patch to address some of the legacy performance
concerns arising when dealing
extensively with java.util.jar.Attributes.Name (mainly when parsing jar
Webrev: http://cr.openjdk.java.net/~redestad/6805750/open.02/
Bug: https://bugs.openjdk.java.net/browse/JDK-6805750
While also picking up a few of the micro-optimizations suggested
(eagerly calculate the hashCode
since it will always be used), the main approach is to set up a small
map of commonly used manifest
attributes, including but not limited to (non-deprecated) ones declared
as constants of Attributes.Name.
For known strings, this can see speed-ups of ~10x of
Attributes.putValue(String, String) and 25x on
Attributes.get(String), while reducing the footprint of typical Manifest
objects[1].
I've also done a few experiments with a concurrent and dynamic backing
storage[2][3], each of which
have some elegant properties (mainly getting similar benefits on
arbitrary attributes), but adding too
much complexity to improve performance of uncommon attributes while
slightly reducing the efficiency
for common ones doesn't really seem worthwhile.
Thanks!
/Claes
[1] http://cr.openjdk.java.net/~redestad/6805750/Attributes.java
[2] http://cr.openjdk.java.net/~redestad/6805750/open.00/ -- reuse
MethodType$ConcurrentWeakInternSet. Nice to reuse some code, but only
gets a 2.5x improvement
since we can't avoid allocation.
[3] http://cr.openjdk.java.net/~redestad/6805750/open.01/ -- create a
custom interning map from
String to WeakEntry<Name>: ~15x get and ~8x putValue perf for any
repeatedly used attribute
name.
