I've added in PutConst and modified the "fib_complex" benchmark to run
on the IR2JVM JIT. Things are looking pretty good.
The benchmark is at the bottom of this email, but it basically just
modifies bench/bench_fib_complex.rb by removing all library and
closure use and having a fixed fib(37) for ten iterations.
It basically does fib, fib with the Fixnum 1 and 2 in local variables
instead of directly, with separate Ruby method calls for + and -, with
1 and 2 looked up from constants, and then a combination of these. The
idea is that local variable use, trivial method calls, and constant
lookups should *ideally* not increase the base time at all.
Here's Ruby 1.9.3 for comparison. Note that each level of complexity
takes another drop from the base performance (which is slower than the
slowest JRuby run, fwiw):
normal fib
4.982727
fib with variables
6.093514
fib with constants
7.154796
fib with additional calls
15.82317
fib with constants and additional calls
17.376949
Oddly enough these numbers seem rather variable and I'm not sure why.
They should stay consistently the same, but perhaps there's some weird
memory effect hitting MRI here:
normal fib
8.621707
fib with variables
11.082168
fib with constants
13.325111
fib with additional calls
29.362528
fib with constants and additional calls
26.660991
ANYWAY...here's JRuby master, normal JIT, Java 7u3:
normal fib
0.805
fib with variables
1.007
fib with constants
2.001
fib with additional calls
1.192
fib with constants and additional calls
2.323
The important thing to notice is that constant lookup for "ONE" and
"TWO" adds a whole second to each iteration. That's largely because
the old JIT doesn't pass along all necessary structures for looking up
constants, so we have to go to a thread-local structure every time
(and push/pop that information on method entry/exit).
Here's IR2JVM, which I'm writing to pass along all necessary
structures for const lookup, etc:
normal fib
1.06
fib with variables
1.511
fib with constants
1.572
fib with additional calls
1.853
fib with constants and additional calls
1.826
In this case, variables and additional calls add a bit of complexity,
which is probably due to there just being more code in the IR version
(which we can improve). However, constants add almost no overhead at
all...they're actually getting to the point of being 100% free here.
That will be very important for typical Ruby applications.
Anyway, good progress.
- Charlie
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