Cache Region Locking for Predictable Latency and SLA Control
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Solution Overview
Problem
Existing cache management systems fail to efficiently manage cache resources, leading to non-deterministic execution times and violations of Service Level Agreements (SLAs) in latency-sensitive applications due to contention and eviction of data or code from the cache.
Innovation Solution
A cache locking mechanism that allows applications to request and control the locking or unlocking of cache regions at various levels, including L1, L2, and L3 caches, and translation lookaside buffers (TLBs), using a programmable interface and a scratch pad to track available regions, ensuring data retention policies and providing feedback on lock requests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cache regions are locked to maintain critical data, then data retention and SLA adherence are improved, but cache resource utilization and flexibility deteriorate
Solution Approach 1:
The patent implements dynamic cache locking where lock status is not fixed but can change based on workload conditions. The system monitors cache access patterns and dynamically adjusts which regions are locked and for how long, allowing the cache to adapt between strict locking (for SLA-critical data) and flexible unlocking (for improved utilization) based on real-time conditions.
Solution Approach 2:
The system changes the locking parameter state by introducing different lock durations and lock types (soft locks vs. hard locks). This allows the same cache region to be locked with different parameters depending on the workload requirements, balancing reliability needs with resource flexibility through parameter adjustment rather than binary locked/unlocked states.
2Loss of time
If cache locking is implemented to reduce non-deterministic execution times, then latency predictability is improved, but system complexity and overhead increase
Solution Approach 1:
The patent introduces a cache locking manager as an intermediary component that handles the complexity of cache locking operations. This mediator sits between the applications and the cache hardware, translating high-level locking requests into specific cache operations, thereby reducing the complexity burden on both the hardware and application layers while maintaining execution time predictability.
Solution Approach 2:
The system implements feedback mechanisms where the cache locking manager monitors cache performance metrics and locking effectiveness, then adjusts locking strategies accordingly. This feedback loop helps optimize the balance between reducing execution time variability and managing system complexity by automatically tuning locking parameters based on observed performance.
3Reliability
If physical isolation is used to guarantee resource availability, then service level objectives are met, but resource utilization and cost efficiency deteriorate
Solution Approach 1:
The patent makes the cache resource universal by implementing multi-tenancy with controlled access. Instead of physically isolating cache resources for different workloads (which would reduce utilization), the system allows multiple workloads to share the same cache under managed locking protocols, enabling the cache to serve multiple functions and tenants while still guaranteeing availability for critical operations through software-based isolation.
Solution Approach 2:
The cache locking manager acts as an intermediary that enables multiple workloads to safely share cache resources. It mediates between competing access requests, implementing virtual isolation through locking mechanisms rather than physical separation, thereby maintaining resource availability guarantees while significantly improving overall cache utilization compared to physical isolation approaches.
Data Source
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AI summary
Examples provide an application program interface or manner of negotiating locking or pinning or unlocking or unpinning of a cache region by which an application, software, or hardware. A cache region can be part of a level-1, level-2, lower or last level cache (LLC), or translation lookaside buffer (TLB) are locked (e.g., pinned) or unlocked (e.g., unpinned). A cache lock controller can respond to a request to lock or unlock a region of cache or TLB by indicating that the request is successful or not successful. If a request is not successful, the controller can provide feedback indicating one or more aspects of the request that are not permitted. The application, software, or hardware can submit another request, a modified request, based on the feedback to attempt to lock a portion of the cache or TLB.