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.
