Which Concurrent Hash Map?

There are several open source java collection libraries which provide concurrent hash map functionality. But which one is faster and suitable for a low latency application?

In this text, following concurrent hash map classes are investigated in terms of their performance:

• ConcurrentHashMap by Oracle (JDK 8)
• ConcurrentHashMap and ConcurrentHashMapUnsafe by Goldman Sachs (GS) Collection (6.1.0) 
• FastMap by Javolution (6.0.0)
• ConcurrentHashMap by Guava (18.0) 

Wherever it is required, these parameters are used:

• Initial Capacity: 16
• Concurrency level: 16
• Load factor: 0.75

Setup

Two kind of tests are done to benchmark Map#put and Map#get() methods of these classes. Following setup is applied:

• As key for maps random generated strings with length of 8 are used.
• For warm up 100K operation is done before benchmarks are done for each tests.
• Each main benchmark is done with various number of tasks (10,100,1K,10K,100K,1M,10M)
• Each benchmark is repeated 5 times and its average is used as result.
• 10 producer (thread) is used to do put/get operations to simulate concurrency.
• To reduce garbage collection (GC) activities, before each benchmark, GC is forced , System.gc() and a large heap size is set.
• Oracle JDK 1.8.0.25 is used
• Test are done on a Redhat , Intel G6 @ 2.93Ghz with 12 cores server.

Results

Following tables and graphs illustrates elapsed time (macroSeconds) of put/get benchmarks.

Put : Classes/Time (macroSecond)	10	100	1000	10000	100000	1000000	10000000
Javolution_FastMap	188	157	292	1684	16857	297025	4228273
Oracle_ConcurrentHashMap	91	119	170	970	12388	207857	2684529
GS_ConcurrentHashMapUnsafe	85	111	259	1017	13290	252151	3053912
GS_ConcurrentHashMap	78	112	205	1060	14051	258071	3104562
Gauva_ConcurrentHashMap	74	93	158	911	12485	205433	2574604

 

Get: Classes/Time (macroSecond)	10	100	1000	10000	100000	1000000	10000000
Javolution_FastMap	98	105	215	1630	15732	215260	2296100
Oracle_ConcurrentHashMap	78	78	115	619	7411	144583	1866310
GS_ConcurrentHashMapUnsafe	86	81	149	960	10342	172114	2204728
GS_ConcurrentHashMap	69	77	146	1119	10322	168585	2027240
Gauva_ConcurrentHashMap	70	71	114	621	7861	129094	1581683

Conclusion

As tables and figures shows that ConcurrentHashMap implementation of Guava and Oracle performs best for put and get operations. This analysis also exposes myths about performance of FastMap by Javolution.

For source code of benchmark, please click here.