Software Transactional Memory Decomposed Instructions Atomicity

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Solution Overview

Problem

Existing software transactional memory systems suffer from performance issues due to indirect methods of implementing transactions, leading to slow operations and substantial overhead, including unnecessary calls and record-keeping that waste memory and system resources.

Innovation Solution

A software transactional memory system utilizing decomposed instructions and runtime optimizations, including a compiler that performs high-level optimizations and extends multi-use header words for per-object housekeeping, along with runtime features like log filtering and garbage collection to enhance performance and atomicity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If indirect method of implementing transactional memory is used, then atomicity is provided, but performance deteriorates due to slow operations and substantial overhead

Engineering Contradiction:

ImproveatomicityVSAvoidperformance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent segments the transactional memory implementation into direct hardware-supported atomic operations rather than indirect software-based approaches. By using hardware transactional memory (HTM) mechanisms, the system divides the problem into manageable atomic units that can be executed directly without complex software overhead, thus maintaining atomicity while improving performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the mechanical software-based transactional memory system with a hardware-based system. By substituting software overhead with hardware-supported atomic operations, the system eliminates unnecessary calls and record-keeping instructions, achieving both atomicity and improved performance through direct hardware execution.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If record-keeping instructions are used in transactional memory, then transaction tracking is achieved, but memory and system resources are wasted

Engineering Contradiction:

Improvetransaction trackingVSAvoidmemory resources

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent extracts the record-keeping functionality from software instructions and relocates it to hardware structures. By taking out the overhead of software-based record-keeping and implementing tracking mechanisms in hardware, the system achieves transaction tracking without consuming excessive memory and system resources.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses hardware-based copying mechanisms to track transactions instead of software record-keeping. By leveraging hardware capabilities to maintain copies of transaction states, the system achieves reliable transaction tracking while minimizing the consumption of memory and system resources compared to software-based approaches.

Inventive Principle:

Principle #26Copying

3Reliability

If unnecessary calls to transactional memory are made, then transaction safety is maintained, but execution efficiency deteriorates

Engineering Contradiction:

Improvetransaction safetyVSAvoidexecution efficiency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent performs preliminary analysis to identify and eliminate unnecessary transactional memory calls before execution. By pre-determining which operations require atomicity guarantees and which do not, the system maintains transaction safety for critical operations while avoiding unnecessary overhead in non-critical sections, thus improving execution efficiency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies partial transactional memory protection only where necessary rather than universally. By implementing transaction safety selectively in critical sections while using non-transactional operations elsewhere, the system maintains adequate transaction safety without the excessive overhead of applying transactional memory to all operations, thereby improving execution efficiency.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS8099726B2Implementing strong atomicity in software transactional memory

Publication Date: 2012.01.17 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

A software transactional memory system is described which utilizes decomposed software transactional memory instructions as well as runtime optimizations to achieve efficient performance. The decomposed instructions allow a compiler with knowledge of the instruction semantics to perform optimizations which would be unavailable on traditional software transactional memory systems. Additionally, high-level software transactional memory optimizations are performed such as code movement around procedure calls, addition of operations to provide strong atomicity, removal of unnecessary read-to-update upgrades, and removal of operations for newly-allocated objects. During execution, multi-use header words for objects are extended to provide for per-object housekeeping, as well as fast snapshots which illustrate changes to objects. Additionally, entries to software transactional memory logs are filtered using an associative table during execution, preventing needless writes to the logs. Finally a garbage collector with knowledge of the software transactional memory system compacts software transactional memory logs during garbage collection.