Hotspot performance
A few days ago Kohsuke Kawaguchi posted a really cool blog entry
titled a "
Deep
dive into assembly code from Java". It's a pile of fascinating
(if gory) assembly code with commentary. Some things to notice:
- Really aggressive inlining
- Even storage allocation & initialization gets inlined -
new T() really is as efficient as C's alloca() (and it beats the
pants off malloc())
- Careful management of cache prefetching
- Deep understanding of variablity between the flavors of x86
machines
- Loop unrolling with warmup/cooldown
- "theorum proving away" of array index checks (and many other
things)
- much cleverness with locks
I've had several run-ins in recent months with crusty C (and a
few Fortran) programmers who say "you must be faking your
benchmarks!". Nope. The HotSpot crew has done a truly great piece
of work.
