The document discusses ultra-low latency applications in Java, focusing on thread communication and memory management. It evaluates different queuing mechanisms, highlighting the Disruptor library for inter-thread messaging, and emphasizes the benefits of off-heap memory allocation to avoid issues with garbage collection. The author also provides links to relevant libraries and offers tips on managing heap sizes.

1. Java for ultra low
latency applications
Rafael Monteiro e Pereira
Software Engineer

2. What is Latency ?
• From the Queueing Theory

3. What is Latency ?
• From the Queueing Theory

4. - Thread Communication
- Memory Management

5. Thread Communication
• Just Create a Queue right ?
• You are sure that you wanna block ?
• https://github.com/real-logic/benchmarks

6. Thread Communication
• Burst (100 messages)
LinkedBlockingQueue 154 μs
ArrayBlockingQueue 56 μs
ConcurrentLinkedQueue 44 μs
Disruptor 3.0 20 μs

7. Thread Communication
• Disruptor (https://github.com/LMAX-Exchange/disruptor )
• Very fast Inter-Thread Message Library
Source: https://martinfowler.com/articles/images/lmax/arch-full.png

8. GC - CMS
Freeze!

9. GC - G1
Freeze!

10. Off-Heap Allocation
• Allocates memory outside the Heap
• HARD ! Really !

11. Off-Heap Allocation
• Copy Object outside the Heap

12. Off-Heap Allocation
• Use a LIB !
• Open HFT -> https://github.com/OpenHFT
• https://github.com/OpenHFT/Java-Thread-Affinity
• https://github.com/OpenHFT/Chronicle-Queue
• https://github.com/OpenHFT/Chronicle-Logger
• Some Tips
• Be careful with big Heap sizes. Usually is not a good idea to go beyond
16 GB on Hotspot.
• Big Heap == Slow GC !!! Consider using off-heap allocation if a lot of
information must be maintained in memory.

13. Obrigado!!!!
Feedback ? Contato ?
E-mail: rafael@monteiro.io
Github: github.com/rafamonteiro
Twitter: @monteiro_io
LinkedIn: lnked.in/rafamonteiro