From Lock-Free to Wait-Free: Linked List. Edward Duong

Transcription

1 From Lock-Free to Wait-Free: Linked List Edward Duong

2 Outline 1) Outline operations of the locality conscious linked list [Braginsky 2012] 2) Transformation concept from lock-free -> wait-free [Timnat 2014]

3 Why Build Concurrent ADTs Leverage multi-cores for speed and throughput i.e., how many operations can we perform at once Achieving performance guarantees for applications such as real-time systems

4 Brief History Wait-Free (WF) and Lock-Free (LF) ADTs: Queue (WF) - Herlihy Linked List (LF) - Valois Hash Tables (LF) - Michael B-Tree (LF) - Bender Locality-conscious Linked List (LF) - Braginsky and Petrank B+Tree (LF) - Braginsky and Petrank

5 Freedom! Increase in guarantees Blocking - Operations use heavy mutual exclusion Terminology from M. Herlihy [1988, 1990]

6 Freedom! Increase in guarantees Obstruction-free - Guaranteed to complete an operation if there is no contention Blocking - Operations are serialized Terminology from M. Herlihy [1988, 1990]

7 Freedom! Lock-free - Even with contention, at least one operation will succeed Increase in guarantees Obstruction-free - Guaranteed to complete an operation if there is no contention Blocking - Operations are serialized Terminology from M. Herlihy [1988, 1990]

8 Freedom! Wait-free - Even with contention, all operations are bounded Lock-free - Even with contention, at least one operation will succeed Increase in guarantees Obstruction-free - Guaranteed to complete an operation if there is no contention Blocking - Operations are serialized Terminology from M. Herlihy [1988, 1990]

9 Freedom! = Wait-free - Even with contention, all operations are bounded Lock-free - Even with contention, at least one operation will succeed Obstruction-free Increase in throughput - Guaranteed to complete an operation if there is no contention Blocking - Operations are serialized Terminology from M. Herlihy [1988, 1990]

10 Linked List: Details Ordered list Stores key / data pairs; no duplicate keys Operations: Search, Insert and Delete Locality Conscious (optimized for cache)

11 Chunks Virtual page...

12 Chunks

13 Search(key) Search for key: 20

14 Search(key) Search for key: 20

15 Search(key) Search for key: 20

16 Search(key) Search for key: 20

17 Insert(key, data) Insert key 18 with data 3

18 Insert(key, data) Insert key 18 with data 3

19 Insert(key, data) Insert key 18 with data 3

20 Insert(key, data) Insert key 18 with data 3

21 Insert(key, data) Insert key 18 with data 3

22 Insert(key, data) Insert key 18 with data 3

23 Insert(key, data) Insert key 18 with data 3

24 Delete(key) Delete key 60

25 Delete(key) Delete key 60

26 Delete(key) Delete key 60

27 Delete(key) Delete key 60

28 Delete(key) Delete key 60

29 Delete(key) Delete key 60

30 Lock-Free -> Wait-Free Can we go from: At least one operation finishing after some finite steps -> any operation is bounded by some finite number of steps? Recipe: Contention Counter Help Queue Modifications to: Search, Insert and Delete

31 Concept Behind Helping Operation 1 Operation 2 Operation 3

32 Concept Behind Helping Enqueue: Operation 1 Operation 2 Operation 3

33 Concept Behind Helping Operation 1 Helping 1 Operation 3

34 Concept Behind Helping Operation 1 Helping 1 Helping 1

35 Concept Behind Helping Success Operation 4 Operation 5

36 Conclusions Adoption is on the rise! Libraries: Boost Noble (Swedish research group) Amino Concurrent Building Blocks

37 Bibliography Braginsky, Anastasia, and Erez Petrank. "Locality-conscious lock-free linked lists." Distributed Computing and Networking. Springer Berlin Heidelberg, Timnat, Shahar, and Erez Petrank. "A Practical Wait-Free Simulation for Lock-Free Data Structures." (2014). Herlihy, Maurice. "A methodology for implementing highly concurrent data objects." ACM Transactions on Programming Languages and Systems (TOPLAS) 15.5 (1993): Valois, John D. "Lock-free linked lists using compare-and-swap." Proceedings of the fourteenth annual ACM symposium on Principles of distributed computing. ACM, Michael, Maged M. "High performance dynamic lock-free hash tables and list-based sets." Proceedings of the fourteenth annual ACM symposium on Parallel algorithms and architectures. ACM, Bender, Michael A., Erik D. Demaine, and Martin Farach-Colton. "Cache-oblivious B-trees." Foundations of Computer Science, Proceedings. 41st Annual Symposium on. IEEE, Braginsky, Anastasia, and Erez Petrank. "A lock-free b+ tree." Proceedinbgs of the 24th ACM symposium on Parallelism in algorithms and architectures. ACM, Herlihy, Maurice P. "Impossibility and universality results for wait-free synchronization." Proceedings of the seventh annual ACM Symposium on Principles of distributed computing. ACM, Libraries: