Bad performance using hash accessors on ConcurrentMap
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Key: JRUBY-5994
URL: https://jira.codehaus.org/browse/JRUBY-5994
Project: JRuby
Issue Type: Bug
Components: Java Integration
Affects Versions: JRuby 1.6.3
Environment: Mac OS 10.7
java version "1.6.0_26"
Java(TM) SE Runtime Environment (build 1.6.0_26-b03-383-11A511)
Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02-383, mixed mode)
Reporter: Martin Kleppmann
Priority: Minor
Google's Guava libraries (http://code.google.com/p/guava-libraries/) contain
some useful collection classes, which I'm using from JRuby. One that I'm using
is an implementation of java.util.concurrent.ConcurrentMap, and JRuby kindly
allows you to access it like a normal Ruby hash. It seems to work correctly,
but unfortunately it's _incredibly_ slow. In the example below, the difference
in runtime between two functionally equivalent lines of code is more than 2
orders of magnitude.
{noformat}
> require 'java'
> require 'guava-r09.jar'
> require 'benchmark'
> map =
> com.google.common.collect.MapMaker.new.maximum_size(200_000).concurrency_level(1).make_map
=> {}
> puts Benchmark.measure{ (1..4000).each{|n| map.put("hello #{n}", 42) unless
> map.contains_key("hello #{n}") } }
0.041000 0.000000 0.041000 ( 0.041000)
=> nil
> map =
> com.google.common.collect.MapMaker.new.maximum_size(2000).concurrency_level(1).make_map
=> {}
> puts Benchmark.measure{ (1..4000).each{|n| map["hello #{n}"] ||= 42 } }
8.461000 0.000000 8.461000 ( 8.461000)
=> nil
{noformat}
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