Martin Buchholz wrote:

I noticed that hotspot changes in jdk 7-b03 had dramatic
effects on the performance of my ArrayList microbenchmark
/net/suttles.sfbay/u/martin/ws/Iter72/test/java/util/ArrayList/RangeCheckMicroBenchmark.java


I notice that some operations are much much faster (good!)
but others are slower:

mergeBench 7-b02 7-b03 jr -dsa -da -server RangeCheckMicroBenchmark.java
==> javac -Xlint:all RangeCheckMicroBenchmark.java
==> java -dsa -da -server RangeCheckMicroBenchmark
Method Millis Ratio vs. 7-b02
get 285 1.000 1.000
set 185 0.651 0.995
get/set 357 1.255 0.811
add/remove at end 3579 12.558 1.676
subList get 253 0.888 0.286
subList set 187 0.656 0.177
subList get/set 334 1.172 0.263
subList add/remove at end 4687 16.444 1.278

subList operations that are not structural changes are
vastly improved, but the structural changes add/remove
are significantly slower. (And the factor of 10 penalty
relative to get/set seems higher than we would like)

It would be good to know whether there is something more hotspot
can do here. If there's interest in the server compiler
team, I could file a bug for the add/remove performance regression.

(I understand there are lots of performance tradeoffs here)

Martin