Non Blocking Algorithms at Traffic Conditions
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This document discusses non-blocking algorithms for controlling shared resources and avoiding race conditions. It describes Treiber's algorithm for implementing a non-blocking stack using compare-and-set operations. Performance comparisons show concurrent and synchronized data structures handling different thread loads. Non-blocking algorithms can utilize all server resources but choose collections based on task. Java 7 generally outperforms Java 6 for concurrent collections.
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Non Blocking Algorithms at Traffic Conditions
- 1. www.ExigenServices.com Non-blocking algorithms at traffic conditions Alina Ziyatova
- 2. Your Reliable IT Business Solution Provider How to control shared resources?
- 3. Your Reliable IT Business Solution Provider Races A B value -> 7 7 + 1 -> 8 value = 8 value -> 7 7 + 1 -> 8 value = 8
- 4. Your Reliable IT Business Solution Provider Increment operation long i = 0; i ++; read modify set
- 5. Your Reliable IT Business Solution Provider Guaranteed: Visibility of changes Atomicity of operations Disadvantages: Throughput public synchronize void method() { // reading or modification } Modifier synchronize
- 6. Your Reliable IT Business Solution Provider The worst case Deadlock Resource 1 Resource 2 Thread 1 Thread 2 I am waiting… I am waiting too…
- 7. Your Reliable IT Business Solution Provider Atomic package AtomicLong i = new AtomicLong(0); i.getAndIncrement(); read modify set
- 8. Your Reliable IT Business Solution Provider Compare & Set operations Read the value Return false Is it differ from expected one? Modify Return true
- 9. Your Reliable IT Business Solution Provider Compare & Set operations Read a value of the variable Perform an intermediate computing Read a value of the variable again and compare with previous one Has the value changed? Yes No
- 10. Your Reliable IT Business Solution Provider Non-blocking algorithms Wait-free Non-blocking Lock-free
- 11. Your Reliable IT Business Solution Provider Stack HEAD Last In – First Out 1 2 null3 2 3
- 12. Your Reliable IT Business Solution Provider Treiber’s algorithm for Stack Node static class Node<E> { final E item; Node<E> next; public Node(E item) { this.item = item; } } 1 2
- 13. Your Reliable IT Business Solution Provider Treiber’s algorithm for Stack import java.util.concurrent.atomic.AtomicReference; public class ConcurrentStack<E> { AtomicReference<Node<E>> head = new AtomicReference<Node<E>>(); //. . . } HEAD 1 2
- 14. Your Reliable IT Business Solution Provider Treiber’s algorithm for Stack HEAD 1 2 3 Push a new Node Read reference Update next field CAS . . . 1 2 2 3 1 0 1 0
- 15. Your Reliable IT Business Solution Provider Treiber’s algorithm for Stack Remove a Node HEAD 1 3 Read reference to next item CAS . . . Read head reference 2 2 2 3 1 2 1
- 16. Your Reliable IT Business Solution Provider Performance comparison 0 2000000 4000000 6000000 8000000 10000000 12000000 14000000 16000000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ConcurrentHashMap ConcurrentSkipListMap SynchronizedHashMap SynchronizedTreeMap Hashtable Number of threads Win7 Enterprise, Intel Core i5-2500 Add probability = 0.6, Remove probability = 0.1 Java version 1.6.0_37
- 17. Your Reliable IT Business Solution Provider Performance comparison Win7 Enterprise, Intel Core i5-2500 Add probability = 0.2, Remove probability = 0.6 0 5000000 10000000 15000000 20000000 25000000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ConcurrentHashMap ConcurrentSkipListMap SynchronizedHashMap SynchronizedTreeMap Hashtable Java version 1.6.0_37 Number of threads
- 18. Your Reliable IT Business Solution Provider Conclusion Choose a type of Collections depending on your task Non-blocking algorithms may consume full resources of a server
- 19. Your Reliable IT Business Solution Provider Performance comparison Win7 Enterprise, Intel Core i5-2500 Add probability = 0.6, Remove probability = 0.1 0 5000000 10000000 15000000 20000000 25000000 30000000 35000000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Java 1.7.0 Java 1.6.0_37 ConcurrentHashMap Number of threads
- 20. Your Reliable IT Business Solution Provider Questions