2nd Benchmark for my concurrency improvements for joda time.

gistfile1.txt

Improving JodaTime Concurrency for DateFormatter
 
   Model Name:	MacBook Pro
   Model Identifier:	MacBookPro11,3
   Processor Name:	Intel Core i7
   Processor Speed:	2,3 GHz
   Number of Processors:	1
   Total Number of Cores:	4
   L2 Cache (per Core):	256 KB
   L3 Cache:	6 MB
   Memory:	16 GB
 
Using JMH and Java 7u45, Tested Single Threaded and with 3 Threads
 
# Before the changes (https://github.com/JodaOrg/joda-time/commit/f17223a4974f3e55097456441d7386735c97ffd6)

    java -jar target/microbenchmarks.jar -f 2 -wi 5 -i 10 -t 1 ".*JodaFormatterBenchmark.*"
    
    Benchmark                                          Mode   Samples         Mean   Mean error    Units
    o.j.t.JodaFormatterBenchmark.DateTimeFormatter    thrpt        20    45279.628      211.954   ops/ms
    o.j.t.JodaFormatterBenchmark.forPattern           thrpt        20    11965.186       48.087   ops/ms
    o.j.t.JodaFormatterBenchmark.print                thrpt        20     2407.998       17.647   ops/ms

    java -jar target/microbenchmarks.jar -f 2 -wi 5 -i 10 -t 3 ".*JodaFormatterBenchmark.*"
    
    Benchmark                                          Mode   Samples         Mean   Mean error    Units
    o.j.t.JodaFormatterBenchmark.DateTimeFormatter    thrpt        20    22353.853      925.899   ops/ms
    o.j.t.JodaFormatterBenchmark.forPattern           thrpt        20     5556.762      101.369   ops/ms
    o.j.t.JodaFormatterBenchmark.print                thrpt        20     6490.630      146.582   ops/ms

Conclusion: The synchronization hurts multithreading performance, reducing efficiency to 50%. Only printing scales, as it uses the array based STYLE_CACHE.

# After this change (https://github.com/CodingFabian/joda-time/tree/avoid_lock_contention_formatter_cache)

    java -jar target/microbenchmarks.jar -f 2 -wi 5 -i 10 -t 1 ".*JodaFormatterBenchmark.*"
    
    Benchmark                                          Mode   Samples         Mean   Mean error    Units
    o.j.t.JodaFormatterBenchmark.DateTimeFormatter    thrpt        20   485731.372     5084.285   ops/ms
    o.j.t.JodaFormatterBenchmark.forPattern           thrpt        20    40250.715      516.932   ops/ms
    o.j.t.JodaFormatterBenchmark.print                thrpt        20     2392.888       32.233   ops/ms

    java -jar target/microbenchmarks.jar -f 2 -wi 5 -i 10 -t 3 ".*JodaFormatterBenchmark.*"
    
    Benchmark                                          Mode   Samples         Mean   Mean error    Units
    o.j.t.JodaFormatterBenchmark.DateTimeFormatter    thrpt        20  1397938.775     7000.980   ops/ms
    o.j.t.JodaFormatterBenchmark.forPattern           thrpt        20   116386.948     2117.401   ops/ms
    o.j.t.JodaFormatterBenchmark.print                thrpt        20     6600.845      101.646   ops/ms

Conclusion: `DateTimeFormat.fullDate()` gains an order of magnitude improvement due to change from LinkedHashMap, other parts gain 3-4 times improvement and scale with number of concurrent threads.