Which Problems Does a Multi-Language Virtual Machine Need to Solve in the Multicore/Manycore Era?
- 1. Which Problems Does a Mul$-‐Language Virtual Machine Need to Solve in the Mul$core/Manycore Era? Stefan Marr Ma8as De Wael, Michael Haupt, Theo D’Hondt VMIL Workshop 2011 2011-‐10-‐24
- 2. VMs today Performance Memory Management F# MulJ-‐Language Eco System PlaLorm Independent 25/10/11 2
- 3. What do we need in the MulJcore/Manycore Era? 25/10/11 3
- 4. Two Dimensions Processor Design Concurrency Models Actors STM DataFlow Fork/Join 25/10/11 4
- 5. Processors and Concurrency Models VM? !&'()* !&'()* !"#$%!&'()* 6$4&)78()&%9&4,(): !&'()* !&'()* !"#$%!&'()* 25/10/11 +&,%-()&. !"$*%-()&. 5 ./")&0%'&'()* 1")#(2.%0#33&)&$4%0&.#5$.
- 6. WHAT ARE THE RELEVANT CHANGES AT THE HARDWARE-‐LEVEL? 25/10/11 6
- 7. Brawny vs. Wimpy • High sequenJal • Weak sequenJal performance performance • Few in numbers • High in numbers 25/10/11 7
- 8. And everything in-‐between! Brawny Hybrid Wimpy IBM Power7 Intel MIC Intel i7 AMD Fusion Cell B.E. Nvidia Fermi 25/10/11 8
- 9. Cores vs. Threads vs. Shared PUs Source: AMD 25/10/11 9
- 10. Memory and CommunicaJon Nehalem Cache Hierarchy Four Processor Setup CommunicaJon implicit via memory Source: Intel 25/10/11 10
- 11. Memory and CommunicaJon TILEPro64 Source: Tilera 25/10/11 11
- 12. What do VMs need to account for? • Appropriate uJlizaJon – Varying performance of cores/units? – Caches and simultaneous mul,threading? • Non-‐uniform memory and communicaJon – Cache hierarchies? – Explicit inter-‐core communicaJon? 25/10/11 12
- 13. Actors STM DataFlow Fork/Join WHAT ARE TYPICAL IMPLEMENTATION PROBLEMS OF CONCURRENCY MODELS? 25/10/11 13
- 14. EncapsulaJon IMPORTANT: Messages can actor BreakEncapsulation: be any kind of object but have to be immutable. Scala def main_loop(self): can’t enforce immutability receive: (yet) so this has to be by convenJon. (Message) => Message.msg = "broken" JCSP: obj-‐by-‐ref, no warning # main Kilim: zero-‐copy type system msg = Message("Hello World!") not “reflecJon-‐proof” broken ! (msg) Clojure: STM + pure Java Agents + pure Java # wait print msg.msg Swing UI: “The single-‐ thread rule” 25/10/11 14
- 15. Scheduling Guarantees Fork/Join Actors PrioriJzed Tasks work-‐stealing fair scheduling priority-‐based scheduling 25/10/11 15
- 16. Immutability Source: Star Wars Episode V: The Empire Strikes Back. 25/10/11 16
- 17. Crossing Borders and Language-‐Levels jThread.sortedSet = FarRefWrapper(sortSet) e a jThread.sortedSet .add(FarRefWrapper(e)) e.compareTo(*) add(e) // add(fr_e) (wrapper semantics) fr_e.compareTo(obj) { return send_wait(e, compareTo, obj) sortedSet } Language/ApplicaJon-‐Level ImplementaJon/Meta-‐Level 25/10/11 17
- 18. What do VMs need to account for? • Enforcing language semanJcs? • Flexible concurrent encapsulaJon? – What is the relaJon to immutability? • Enforceable scheduling guarantees? • Normal vs. reflecJve operaJons? 25/10/11 18
- 19. What do VMs need to account for? Processor Design Concurrency Models Actors STM DataFlow Fork/Join 25/10/11 19
- 20. What do VMs need to account for? Processor Design Concurrency Models • Appropriate uJlizaJon • Flexible concurrent – Varying performance? encapsulaJon? – Hyperthreads? – Flexible Immutability? • Non-‐uniform memory and • Enforceable scheduling communicaJon guarantees? – Cache hierarchies? • Normal vs. reflecJve – Explicit inter-‐core operaJons? communicaJon? 25/10/11 20