Transactional Atomic Operation Batching for Lower-Latency Processors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lock instructions in out-of-order processors cause high latency and pipeline stalls due to their requirement for previous instructions to retire before execution, leading to degraded application performance and code bloat from needing separate transaction paths.
Innovation Solution
Implementing a processor architecture that treats lock-load and store-unlock operations as normal load/store operations within a transaction, eliminating the need for separate fallback paths and reducing latency by ensuring atomicity through transactional execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lock instructions are used for atomic operations in out-of-order processors, then atomicity is ensured, but latency increases to 20 cycles and pipeline stalls occur
Solution Approach 1:
The patent replaces the traditional lock instruction mechanism (which requires retirement ordering and causes pipeline stalls) with a transactional memory mechanism that uses normal load/store instructions. The transactional system ensures atomicity through hardware-supported transactional execution rather than software locking, eliminating the need for instruction retirement ordering constraints and reducing latency from 20 cycles to 1-2 cycles.
Solution Approach 2:
The patent changes the execution model parameter from retirement-ordered execution (required by traditional locks) to out-of-order transactional execution. By modifying how atomicity is enforced—shifting from a retirement-based mechanism to a transactional memory mechanism—the system maintains atomicity while allowing instructions to execute out-of-order, thereby reducing latency.
2Reliability
If separate fallback paths are implemented for transactional operations, then atomicity is maintained, but code size increases due to code bloat
Solution Approach 1:
The patent extracts and eliminates the need for separate fallback paths by using hardware-supported transactional execution. The transactional memory system provides atomicity guarantees natively, removing the requirement for alternative execution paths and reducing code size.
Solution Approach 2:
The patent makes normal load/store instructions universal by enabling them to execute within transactions and provide atomicity guarantees. This eliminates the need for specialized lock instructions and separate fallback paths, as the same instructions can be used for both normal and atomic operations depending on transaction context.
3Stability of the object's composition
If lock instructions require previous instructions to retire before execution, then execution ordering is controlled, but pipeline stalls and performance degradation occur
Solution Approach 1:
The patent substitutes the retirement-based execution control mechanism with transactional execution control. Instead of requiring instructions to retire before execution (which causes pipeline stalls), the transactional system uses hardware-supported transactional boundaries to control ordering, allowing out-of-order execution while maintaining correctness and improving productivity.
Data Source
AI summary
Techniques for batching atomic operations within a transaction are described. In some examples, program code includes a transaction and instructions within that transaction that indicate a lock is to be used. In some examples, the lock(s) is/are ignored for instructions within the transaction and the lock(s) is/are used when the transaction does not exist (e.g., the fallback path is the same as the transaction path).