Split Hardware Transactions for Nested Atomic Blocks

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Solution Overview

Problem

Concurrent software designs face challenges in ensuring atomicity of operations across threads without relying on locks, which can lead to deadlocks and performance issues, and traditional transactional memory implementations do not efficiently support nested atomic blocks or non-hardware-transactionable operations.

Innovation Solution

The implementation of split hardware transactions, which split an atomic block into segments executed using separate hardware transactions, allowing for the execution of nested code and non-hardware-transactionable operations within a single atomic transaction, utilizing thread-local buffers for logging memory accesses and ensuring atomicity through hardware transactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional hardware transactional memory is used, then atomicity is achieved, but nested atomic blocks and non-hardware-transactionable operations cannot be supported

Engineering Contradiction:

Improvesupport for nested atomic blocks and non-hardware-transactionable operationsVSAvoidatomicity guarantee

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the atomic block execution into multiple hardware transactions separated by software transactional barriers. Each segment can be executed as a separate hardware transaction, allowing nested atomic blocks and non-hardware-transactionable operations to be integrated while maintaining atomicity through the barrier mechanism that ensures proper synchronization and consistency across segments.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If software transactional memory is used, then flexibility and support for all operations are achieved, but performance is reduced

Engineering Contradiction:

Improvesupport for all operations including context switches and interruptsVSAvoidexecution speed

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent merges hardware transactional memory segments with software transactional barriers to create a hybrid system. The hardware transactions provide fast execution for memory operations, while the software barriers handle complex operations like context switches and interrupts. This combination achieves both high performance and full operational flexibility.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If locks are used to ensure atomicity, then thread safety is achieved, but deadlocks and performance issues arise

Engineering Contradiction:

Improvethread safetyVSAvoidthread throughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces the mechanical lock-based synchronization mechanism with a hardware transactional memory system enhanced by software barriers. This substitution eliminates the deadlock problem inherent in locks while maintaining thread safety, and improves throughput by allowing concurrent execution without lock contention.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Productivity

If hardware transactions are used, then performance is improved, but non-hardware-transactionable operations cause transaction abortion

Engineering Contradiction:

Improveexecution speedVSAvoidtransaction completion

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces software transactional barriers as preliminary actions that prepare for and manage non-hardware-transactionable operations. These barriers are placed strategically to pause hardware transactions before NHT operations, allowing them to complete successfully without causing abortion, and then resume transactions afterward to maintain atomicity.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7516366B2System and method for executing nested atomic blocks using split hardware transactions

Publication Date: 2009.04.07 ORACLE AMERICAN INC

AI summary

Split hardware transaction techniques may support execution of serial and parallel nesting of code within an atomic block to an arbitrary nesting depth. An atomic block including child code sequences nested within a parent code sequence may be executed using separate hardware transactions for each child, but the execution of the parent code sequence, the child code sequences, and other code within the atomic block may appear to have been executed as a single transaction. If a child transaction fails, it may be retried without retrying the parent code sequence or other child code sequences. Before a child transaction is executed, a determination of memory consistency may be made. If a memory inconsistency is detected, the child transaction may be retried or control may be returned to its parent. Memory inconsistencies between parallel child transactions may be resolved by serializing their execution before retrying at least one of them.