Instruction Prefetch Mechanism for Cache Miss Feedback

Solution Overview

Problem

Current graphics processing systems face performance issues due to sub-optimal insertion of prefetch instructions, as they lack direct feedback on cache misses, leading to either excessive or insufficient prefetching, which worsens memory system pressure and cache-miss rates.

Innovation Solution

An instruction prefetch mechanism that tracks cache misses and provides feedback to the compiler to recompile and insert prefetch instructions for instructions exceeding a predetermined miss threshold, ensuring timely and effective prefetching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If prefetch instructions are inserted without knowledge of exact cache misses, then prefetching can be performed, but cache-miss rate remains high and memory system pressure increases

Engineering Contradiction:

Improvecache hit rateVSAvoidmemory access performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent implements a feedback mechanism where cache miss statistics are collected and used to guide prefetch instruction insertion. The system tracks which instructions cause cache misses and feeds this information back to the compiler, which then adjusts prefetch strategies accordingly. This closed-loop approach enables data-driven optimization of prefetching to improve cache hit rates while reducing memory pressure.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies preliminary action by inserting prefetch instructions before the actual memory access occurs. The compiler analyzes program execution patterns and inserts prefetch instructions in advance for instructions that are likely to cause cache misses, allowing data to be loaded into cache before it is actually needed, thus improving hit rates and reducing latency.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If more prefetch instructions are inserted, then cache hit chances increase, but memory system pressure and execution time increase

Engineering Contradiction:

Improvecache hit rateVSAvoidexecution time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies partial action by selectively inserting prefetch instructions only for instructions that have been identified as causing cache misses, rather than uniformly inserting prefetches throughout the entire program. This targeted approach ensures that prefetching is applied only where beneficial, improving cache hit rates for critical instructions while avoiding unnecessary prefetches that would waste execution time and increase memory pressure.

Inventive Principle:

Principle #16Partial or excessive action

3Quantity of substance

If prefetch instructions are inserted aggressively, then more data is pre-loaded, but memory system pressure increases and cache-miss rate worsens

Engineering Contradiction:

Improvedata pre-loadedVSAvoidmemory system pressure

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent applies partial action by selectively inserting prefetch instructions only for instructions that have been identified as causing cache misses, rather than uniformly inserting prefetches throughout the entire program. This targeted approach ensures that prefetching is applied only where beneficial, improving cache hit rates for critical instructions while avoiding unnecessary prefetches that would waste execution time and increase memory pressure.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent implements a feedback mechanism where cache miss statistics are collected and used to guide prefetch instruction insertion. The system tracks which instructions cause cache misses and feeds this information back to the compiler, which then adjusts prefetch strategies accordingly. This closed-loop approach enables data-driven optimization of prefetching to improve cache hit rates while reducing memory pressure.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12164430B2Instruction prefetch mechanism

Publication Date: 2024.12.10 INTEL CORP

AI summary

An apparatus to facilitate data prefetching is disclosed. The apparatus includes a cache, one or more execution units (EUs) to execute program code, prefetch logic to maintain tracking information of memory instructions in the program code that trigger a cache miss and compiler logic to receive the tracking information, insert one or more pre-fetch instructions in updated program code to prefetch data from a memory for execution of one or more of the memory instructions that triggered a cache miss and download the updated program code for execution by the one or more EUs.