A talk on JRuby 900 delivered at the Taipei Ruby User's Group hosted by 5xRuby on Dec 1, 2015.

1. JRuby 9000
Charles O. Nutter
JRuby; Red Hat

2. JRuby is Ruby…
(on the JVM...shhhh!)

3. Why the JVM is great
for Ruby!

4. Shoulders of Giants
JVMJ. RoseJ. RoseJ. RoseJ. RoseJ. RoseJ. RoseJ. RoseJ. RoseJ. Rose
Hiro
Marcin
Nahi
Subbu Douglas
Christian Dmitry
Tom
Charlie
JRuby

5. All the stuff!
JVMJ. RoseJ. RoseJ. RoseJ. RoseJ. RoseJ. RoseJ. RoseJ. RoseJ. Rose
Garbage
Collection
Native JIT
Profiled
Optimizations
Native
Threading
Tooling Cross Platform

6. Can leverage Java
Ecosystem
47k libraries in Maven
Hadoop EHCache
Selenium
Sitemesh
Lucene
Neo4j
JMonkeyEngine

7. Polyglot
Clojure Scala
Groovy
Jython
Rhino/Nashorn/
DynJS (JavaScript)
Micro Focus JVMVisual COBOL
Java

8. red/black tree, pure Ruby versus native
ruby-2.0.0 + Ruby
ruby-2.0.0 + C ext
jruby + Ruby
Runtime per iteration
0 0.75 1.5 2.25 3
0.29s
0.51s
2.48s

9. GC

10. GC Matters
• Applications grow over time
• Ruby is very object-heavy
• Multiprocess multiplies the problem
• You will eventually have issues

11. gc_demo.rb
• Heavy GC, mix of old and young
• Steadily growing heap use

12. class Simple
attr_accessor :next
end
top = Simple.new
puts Benchmark.measure {
outer = 10
total = 100000
per = 100
outer.times do
total.times do
per.times { Simple.new }
s = Simple.new
top.next = s
top = s
end
end
}

13. 0
750
1500
2250
3000
GC count
Ruby 2.1.1 JRuby

14. 1
10
100
1000
10000
GC count
Ruby 2.1.1 JRuby

15. 0s
0.45s
0.9s
1.35s
1.8s
GC time %
Ruby 2.2.2 JRuby

16. Threads

17. Real Parallellism
• Ruby thread = JVM thread = native thread
• One process can use all cores
• One server can handle all requests

18. Ruby 2.2
unthreaded
Ruby 2.2
threaded
JRuby
unthreaded
JRuby
threaded

19. Per-iteration time versus thread count
0.2s
0.35s
0.5s
0.65s
0.8s
one thread two threads three threads four threads
threaded_reverse

20. Tools

21. Profiling
• Java profilers
• VisualVM,YourKit, NetBeans, JXInsight
• jruby [--profile | --profile.graph]
• JVM command-line profilers

22. VisualVM
• CPU, memory, thread monitoring
• CPU and memory profiling
• VisualGC
• Heap analysis

26. Scripting Java

27. Purugin
• Nearly 100% Ruby wrapper
• Thin shim makes Java feel very Ruby-like
• It’s Minecraft!

28. Egg Madness

29. Egg Madness
class EggMadnessPlugin
include Purugin::Plugin
description 'EggMadness', 0.1
def on_enable
event(:player_egg_throw) do |e|
e.hatching = true
e.num_hatches = 50
e.hatching_type = :chicken
end
end
end

30. 1.7.23
JRuby Roadmap
mastermaster
1.7.3 1.7.4 1.7.5
1.7.6
...
1.7.7 1.7.22
...
9.0.4
2.2
1.8, 1.9
jruby-1_7jruby-1_7jruby-1_7
master
2.2
1.8, 1.9
End of week
Last Friday

31. JRuby 9000
• Ruby 2.2
• New runtime (IR)
• Major IO and Encodings overhaul

32. “It’s over 9000!!!!”

33. Now What?

34. PERFORMANCE
WORK
topic of this talk
Now and into not so distant future!

35. Recent Wins
• JITable blocks
• define_method performance
• Reduced-cost transient exceptions

36. Block Jitting
• JRuby 1.7 only jitted methods
• Not free-standing procs/lambdas
• Not define_method blocks
• Easier to do now with 9000's IR
• Blocks JIT now in 9.0.4.0

37. Jitting is Winning
Performance of define_method in loaded file
0k iters/s
750k iters/s
1500k iters/s
2250k iters/s
3000k iters/s
MRI JRuby 9.0.1.0 JRuby 9.0.4.0
normal method define_method method
ruby -e 'load "bench_define_method.rb"'

38. define_method
Convenient for metaprogramming,
but blocks have more overhead than methods.
define_method(:add) do |a, b|
a + b
end
names.each do |name|
define_method(name) { send :"do_#{name}" }
end

39. :-(
0k iters/s
1000k iters/s
2000k iters/s
3000k iters/s
4000k iters/s
MRI JRuby 9.0.1.0
def define_method
define_method w/ capture

40. Optimizing define_method
• Noncapturing
• Treat as method in compiler
• Ignore surrounding scope
• Capturing (future work)
• Lift read-only variables as constant

41. Getting Better!
0k iters/s
1000k iters/s
2000k iters/s
3000k iters/s
4000k iters/s
MRI JRuby 9.0.1.0 JRuby 9.0.4.0
def define_method
define_method w/ capture

42. Reduced-cost Exceptions
• Backtrace cost isVERY high on JVM
• Heavily optimized, lots of work to build
• Exceptions frequently ignored
• ...or used as flow control (shame!)
• If ignored, backtrace is not needed!

43. Postfix Antipattern
foo rescue nil
Exception raised
StandardError rescued
Exception ignored
Result is simple expression, so exception is never visible.

44. csv.rb Converters
Converters = { integer: lambda { |f|
Integer(f.encode(ConverterEncoding)) rescue f
},
float: lambda { |f|
Float(f.encode(ConverterEncoding)) rescue f
},
...
All trivial rescues, no traces needed.

45. Simple rescue
Improvement
0
150000
300000
450000
600000
Iters/second
524,475
10,700

46. Nearly Two Magnitudes!
1
10
100
1000
10000
100000
1000000
Iters/second
524,475
10,700

47. New Runtime?
• AST to semantic representation
• Traditional Compiler Design
• Wanted Architectural longevity

48. Lexical
Analysis
Parsing
Semantic
Analysis
Optimization
Bytecode
Generation
Interpret
AST
IR Instructions
CFG DFG ...
JRuby 1.7.x
9000+
Dalvik
Generation
...

49. def foo(a, b)
c = 1
d = a + c
end
0 check_arity(2, 0, -1)
1 a = recv_pre_reqd_arg(0)
2 b = recv_pre_reqd_arg(1)
3 %block = recv_closure
4 thread_poll
5 line_num(1)
6 c = 1
7 line_num(2)
8 %v_0 = call(:+, a, [c])
9 d = copy(%v_0)
10 return(%v_0)
Register-based
3 address format
IR InstructionsSemantic
Analysis

50. -Xir.passes=LocalOptimizationPass,
DeadCodeElimination
def foo(a, b)
c = 1
d = a + c
end
0 check_arity(2, 0, -1)
1 a = recv_pre_reqd_arg(0)
2 b = recv_pre_reqd_arg(1)
3 %block = recv_closure
4 thread_poll
5 line_num(1)
6 c = 1
7 line_num(2)
8 %v_0 = call(:+, a, [c])
9 d = copy(%v_0)
10 return(%v_0)
Optimization

51. def foo(a, b)
c = 1
d = a + c
end
0 check_arity(2, 0, -1)
1 a = recv_pre_reqd_arg(0)
4 thread_poll
5 line_num(1)
6 c = 1
7 line_num(2)
8 %v_0 = call(:+, a, [c])
9 d = copy(%v_0)
10 return(%v_0)
0 check_arity(2, 0, -1)
1 a = recv_pre_reqd_arg(0)
4 thread_poll
5 line_num(1)
6 c =
7 line_num(2)
8 %v_0 = call(:+, a, [ ])
9 d = copy(%v_0)
10 return(%v_0)
1
0 check_arity(2, 0, -1)
1 a = recv_pre_reqd_arg(0)
4 thread_poll
5 line_num(1)
7 line_num(2)
8 %v_0 = call(:+, a, [1])
9 d = copy(%v_0)
10 return(%v_0)
Optimization -Xir.passes=LocalOptimizationPass,
DeadCodeElimination

52. 0 check_arity(2, 0, -1)
1 a = recv_pre_reqd_arg(0)
4 thread_poll
5 line_num(1)
7 line_num(2)
8 %v_0 = call(:+, a, [1])
9 d = copy(%v_0)
10 return(%v_0)
0 check_arity(2, 0, -1)
1 a = recv_pre_reqd_arg(0)
4 thread_poll
7 line_num(2)
8 %v_0 = call(:+, a, [1])
9 d = copy(%v_0)
10 return(%v_0)
Optimization -Xir.passes=LocalOptimizationPass,
DeadCodeElimination

53. Inlining
• 500 pound gorilla of optimizations
• shove method/closure back to callsite
• eliminate stack frame
• eliminate parameter passing/return
• eliminate additional allocation
Optimization

54. Today’s Inliner
def decrement_one(i)
i - 1
end
i = 1_000_000
while i > 0
i = decrement_one(i)
end
def decrement_one(i)
i - 1
end
i = 1_000_000
while i < 0
if guard_same? self
i = i - 1
else
i = decrement_one(i)
end
end

55. Numeric Specialization
• Everything's an object
• JVM has only references and primitives
• Not compatible in bytecode
• Need to optimize numerics as primitive

56. def looper(n)
i = 0
while i < n
do_something(i)
i += 1
end
end
Cached object
Call with i
New Fixnum i + 1
Probably a Fixnum?

57. def looper(n)
i = 0
while i < n
do_something(i)
i += 1
end
end
def looper(long n)
long i = 0
while i < n
do_something(i)
i += 1
end
end
Specialize n, i to long
def looper(n)
i = 0
while i < n
do_something(i)
i += 1
end
end
Deopt to object version if n or i + 1 is not Fixnum

58. JVM Futures
• We're good friends with OpenJDK folks
• Working to improve JVM as well
• FFI being added at JVM level
• AOT compilation for startup perf

59. FFI in JVM
• Project Panama (JEP-191)
• Native support for FFI
• Code generators for binding
• JIT support for calling
• API support for userland

60. User Code
JNI call
JNI impl
Target Library
Java
C/native

61. User Code
JNR stub
JNI call
JNI impl
libffi
Target Library
Java
C/native

62. User Code
Panama
Target Library
Java
C/native
JIT knows about
both sides

63. JIT Magic
callq <getpid address> ; - libSystem.B.dylib
;*invokeinterface getpid
; - GetPidJNRExample::benchGetPid@13 (line 26)
; {optimized virtual_call}
Direct call from JITed Ruby code

64. Startup Time
• By far our greatest challenge
• Everything starts cold: parser, interpreter,
compiler, core classes, boot logic
• Increasing amount of Ruby in JRuby
• Aggravates the problem

65. JRuby Startup
C Ruby
JRuby
Time in seconds (lower is better)
0s 3.5s 7s 10.5s 14s
-e 1 gem --list rake -T in Rals app

66. --dev
• Disables JRuby JIT
• Sets JVM to reduced optimization mode
• 50% reduction in startup time
• Much lower peak perf

67. JRuby --dev
C Ruby
JRuby
JRuby --dev
Time in seconds (lower is better)
0s 3.5s 7s 10.5s 14s
-e 1 gem --list rake -T in Rals app

68. AOT
• Precompile JVM bytecode to native
• Focus on hot code
• Save original structure for optimization
• Get JRuby running native right away
• AOT compile Ruby to native in future

69. Getting There
C Ruby
JRuby
JRuby --dev
Non-opto AOT
Opto AOT
Time in seconds (lower is better)
0s 3.5s 7s 10.5s 14s
rake -T in Rails app

70. AOT Future
• AOT might be available in Java 9
• Many tweaks we can make to help it
• Ideal: all code run at boot runs native
• Should get closer to MRI

73. ThankYou
• @headius
• @tom_enebo
• http://jruby.org