Hybrid STM/HTM for Nested Transactions on OpenJDK
0 likes359 views
Hybrid STM/HTM for Nested Transactions on OpenJDK aims to accelerate STM using HTM where possible. It presents a hybrid transactional memory system using both STM and HTM that supports flat and nested transactions. The key aspects are: 1) It introduces a hybrid transaction protocol that allows STM and HTM transactions to co-exist and detect conflicts. 2) It modifies OpenJDK to add native HTM support via Intel TSX and makes modifications to HotSpot's compilers to integrate HTM. 3) Microbenchmarks show the hybrid system achieves much higher throughput than pure STM, especially for open nested transactions where HTM avoids most STM overhead. Throughput
Hybrid STM/HTM for Nested Transactions on OpenJDK
- 1. Hybrid STM/HTM for Nested Transactions on OpenJDK Keith Chapman Purdue U Tony Hosking ANU/Data61, Purdue U Eliot Moss UMass
- 2. Motivation STM has been around for ages • But STM is slow Commodity hardware for transactions available now • But HTM approaches are only best effort Out goal: Accelerate STM with HTM when possible
- 3. Nested Transactions Allow composition of transactions Two flavors • Closed Nested Transactions • HTM inside STM not useful; must do all the same work • Open Nested Transactions • HTM inside STM avoids most TM work – HTM well-suited!
- 4. XJ: Transactional Java XJ Language • Supports flat and closed/open/boosted nested transactions The implementation supports hybrid transactions • HTM support via Intel TSX • HTM and STM can co-exist Uses an Optimistic-reads / Pessimistic-writes protocol
- 5. TM Metadata Txn Log 0 0Version # 0 0 0Txn ID 1 One metadata word for every object
- 6. STM Transaction Protocol (Read) T1 Log 0 00 0
- 7. STM Transaction Protocol (Read) T1 Log 0 00 0 Check Mode
- 8. STM Transaction Protocol (Read) T1 Log 0 0 0 0 T1 Read
- 9. STM Transaction Protocol (Read) T1 Log 0 0 0 0 T1 Validate
- 10. STM Transaction Protocol (Read) T1 Log 0 0 T1 Commit
- 11. 0 0 STM Transaction Protocol (Write) T1 Log
- 12. 0 0 STM Transaction Protocol (Write) T1 Log Check Mode
- 13. T1 1 0 0 STM Transaction Protocol (Write) T1 Log T1 Write
- 14. T1 1 0 0 STM Transaction Protocol (Write) T1 Log T1 Write
- 15. T1 1 0 0 STM Transaction Protocol (Write) T1 Log T1 Write
- 16. T1 11 0 STM Transaction Protocol (Write) T1 Log T1 Commit
- 17. STM Conflict Detection T1 Log 0 00 0 T2 Log 0 0
- 18. STM Conflict Detection T1 Log 0 0 0 0 T2 Log 0 0 T1 Read
- 19. STM Conflict Detection T1 Log 0 0 0 0 T2 Log 0 0 T2 Write T2 1
- 20. STM Conflict Detection T1 Log 0 0 0 0 T2 Log 0 0 T1 Validate T2 1
- 21. STM Conflict Detection T1 Log 0 0 T2 Log 0 0 T1 Abort T2 1
- 22. Hybrid Transaction Protocol STM – HTM conflicts detected by lock word accesses • Explicit XABORT if locked by another transaction • HTM reads – Read the metadata word • STM writes modify the metadata word • Causes HTM to abort • HTM writes – Increment version number • Causes STM read invalidation / HTM abort
- 24. Abstract Locks for STM Open / Boosted Atomic Method Body Acquire abstract locks Release abstract locks If top level transaction Open / Boosted Atomic Method Body Acquire abstract locks Log abstract locks If nested transaction Log undo operations
- 25. Abstract Locks for Hybrid TM Open / Boosted Atomic Method Body Validate abstract locks Open / Boosted Atomic Method Body Acquire abstract locks Log abstract locks If top level is HTM Log undo operations
- 26. Why Validation Works • HTM vs STM • If abstract locks conflict they must touch some same physical words in the abstract locking data structure — otherwise they could not detect the conflict Open / Boosted Atomic Method Body Validate abstract locks
- 27. Why Validation Works • HTM vs STM • If abstract locks conflict they must touch some same physical words in the abstract locking data structure — otherwise they could not detect the conflict • HTM vs HTM • No conflict in the locking data structure because all accesses to it are reads • Any real conflicts that exist will occur on the actual data structure Open / Boosted Atomic Method Body Validate abstract locks
- 28. STM and HTM Methods STM needs logging HTM doesn't Different actions during read/write Different actions for abstract locks HTM should fall back to STM
- 29. STM and HTM Methods STM needs logging HTM doesn't Different actions during read/write Different actions for abstract locks HTM should fall back to STM Maintain separate HTM and STM versions of methods
- 31. STM Method Variants Original (Non-txnal) Can call A B
- 32. STM Method Variants Original (Non-txnal) Top-level Txn STM Can call A B
- 33. STM Method Variants Original (Non-txnal) Top-level Txn STM Can call A B
- 34. STM Method Variants STM Transactionalized Original (Non-txnal) Top-level Txn STM Can call A B
- 35. STM Method Variants STM Transactionalized Original (Non-txnal) Top-level Txn STM Can call A B
- 36. STM Method Variants STM Transactionalized Original (Non-txnal) New nested Txn STM Top-level Txn STM Can call A B
- 37. STM Method Variants STM Transactionalized Original (Non-txnal) New nested Txn STM Top-level Txn STM Can call A B
- 38. STM Method Variants STM Transactionalized Original (Non-txnal) New nested Txn STM Top-level Txn STM Can call A B
- 39. STM Method Variants STM Transactionalized Original (Non-txnal) New nested Txn STM Top-level Txn STM Can call A B
- 40. Hybrid TM Method Variants Original (Non-txnal)
- 41. Hybrid TM Method Variants Original (Non-txnal)Can call A B
- 42. Hybrid TM Method Variants Router Original (Non-txnal)Can call A B
- 43. Hybrid TM Method Variants Router Original (Non-txnal)Can call A B
- 44. Hybrid TM Method Variants Top-level Txn STM Router Original (Non-txnal)Can call A B
- 45. Hybrid TM Method Variants Top-level Txn HTM Top-level Txn STM Router Original (Non-txnal)Can call A B
- 46. Hybrid TM Method Variants HTM Transactionalized Top-level Txn HTM Top-level Txn STM Router Original (Non-txnal)Can call A B
- 47. Hybrid TM Method Variants HTM Transactionalized Top-level Txn HTM Top-level Txn STM Router Original (Non-txnal)Can call A B
- 48. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM Top-level Txn STM Router Original (Non-txnal)Can call A B
- 49. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM Top-level Txn STM Router Original (Non-txnal)Can call A B
- 50. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM Top-level Txn STM Router Original (Non-txnal)Can call A B
- 51. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM STM Transactionalized Top-level Txn STM Router Original (Non-txnal)Can call A B
- 52. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM STM Transactionalized Top-level Txn STM Router Original (Non-txnal)Can call A B
- 53. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM STM Transactionalized Top-level Txn STM New nested Txn STM Router Original (Non-txnal)Can call A B Parent is closed A B
- 54. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM STM Transactionalized Top-level Txn STM New nested Txn STM Router Original (Non-txnal)Can call A B Parent is closed A B
- 55. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM STM Transactionalized Top-level Txn STM New nested Txn STM Router Original (Non-txnal)Can call A B Parent is closed A B
- 56. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM STM Transactionalized Top-level Txn STM New nested Txn STM Router Nested Router Original (Non-txnal)Can call A B Parent is closed A B Parent is open A B
- 57. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM STM Transactionalized Top-level Txn STM New nested Txn STM Router Nested Router Original (Non-txnal)Can call A B Parent is closed A B Parent is open A B
- 58. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM New nested Txn HTM STM Transactionalized Top-level Txn STM New nested Txn STM Router Nested Router Original (Non-txnal)Can call A B Parent is closed A B Parent is open A B
- 59. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM New nested Txn HTM STM Transactionalized Top-level Txn STM New nested Txn STM Router Nested Router Original (Non-txnal)Can call A B Parent is closed A B Parent is open A B
- 60. Hybrid TM Method Variants Optimized New nested Txn HTM HTM Transactionalized Top-level Txn HTM New nested Txn HTM STM Transactionalized Top-level Txn STM New nested Txn STM Router Nested Router Original (Non-txnal)Can call A B Parent is closed A B Parent is open A B
- 62. XJ System Architecture XJ source code
- 63. XJ System Architecture XJ source code XJ Compiler standard Java bytecode compile
- 64. XJ System Architecture XJ source code XJ Compiler standard Java bytecode XJ Rewriter bytecode + run-time calls compile load
- 65. XJ System Architecture XJ source code XJ run-time library XJ Compiler standard Java bytecode XJ Rewriter bytecode + run-time calls HTM-enabled JVM compile load run
- 66. XJ System Architecture HTM 4-5 times faster than STM XJ source code XJ run-time library XJ Compiler standard Java bytecode XJ Rewriter bytecode + run-time calls HTM-enabled JVM compile load run
- 67. VM Modifications Kept to a minimum Modifications done on OpenJDK: • Native methods to begin, end, and abort a HW transaction • Made them intrinsic to the HotSpot C1/C2 compilers Had to go through several hoops to get HTM to work with HotSpot’s optimizing compilers
- 68. Results
- 69. Synchrobench Micro-benchmarks to evaluate synchronization performance on various data structures Added ability to run multiple operations within a single transaction (group size) Included XJ versions of the benchmarks • TransactionalFriendlyTreeSet 48-way, Intel Xeon E5-2690 v3 machine with 2 sockets of 12 hyperthreaded cores
- 70. Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Open nestedClosed nested Group size 1 5% Updates
- 71. Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Group size 1 Group size 2 Open nestedClosed nested 5% Updates
- 72. Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Group size 1 Group size 2 Group size 4 Open nestedClosed nested 5% Updates
- 73. Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Group size 1 Group size 2 Group size 4 Group size 8 Open nestedClosed nested 5% Updates
- 74. Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Group size 1 Group size 2 Group size 4 Group size 8 Group size 16 Open nestedClosed nested 5% Updates
- 75. Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Throughput(Normalized) 0 0.2 0.4 0.6 0.8 1 Threads 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Group size 1 Group size 2 Group size 4 Group size 8 Group size 16 Group size 32 Open nestedClosed nested 5% Updates
- 76. 0 50 100 150 200 1 2 4 8 12 16 20 24 28 32 36 40 44 48 1 2 4 8 12 16 20 24 28 32 36 40 44 48 1 2 4 8 12 16 20 24 28 32 36 40 44 48 Group size 1 Group size 2 Group size 4 committedopsandabortedtxns(10 6 ) open htm commits closed htm commits open stm commits closed stm commits htm aborts
- 77. Conclusions STM and HTM can co-exist for nested transactions in Java • Closed nesting — Similar to previous schemes • Open nesting — Novel validation mechanism • Implemented in OpenJDK on Intel TSX — Artifact evaluated
- 78. Conclusions STM and HTM can co-exist for nested transactions in Java • Closed nesting — Similar to previous schemes • Open nesting — Novel validation mechanism • Implemented in OpenJDK on Intel TSX — Artifact evaluated
- 79. Conclusions STM and HTM can co-exist for nested transactions in Java • Closed nesting — Similar to previous schemes • Open nesting — Novel validation mechanism • Implemented in OpenJDK on Intel TSX — Artifact evaluated When it works, HTM is ~4-5× faster than STM
- 80. Conclusions STM and HTM can co-exist for nested transactions in Java • Closed nesting — Similar to previous schemes • Open nesting — Novel validation mechanism • Implemented in OpenJDK on Intel TSX — Artifact evaluated When it works, HTM is ~4-5× faster than STM Open nesting increases the envelope of effectiveness for HTM
- 81. Conclusions STM and HTM can co-exist for nested transactions in Java • Closed nesting — Similar to previous schemes • Open nesting — Novel validation mechanism • Implemented in OpenJDK on Intel TSX — Artifact evaluated When it works, HTM is ~4-5× faster than STM Open nesting increases the envelope of effectiveness for HTM Production VM would need deeper modification