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Method for priority-based cache-line residency

IP.com Disclosure Number: IPCOM000128946D
Publication Date: 2005-Sep-21
Document File: 3 page(s) / 51K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for priority-based cache-line residency. Benefits include improved functionality, improved performance, and improved reliability.

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Method for priority-based cache-line residency

Disclosed is a method for priority-based cache-line residency. Benefits include improved functionality, improved performance, and improved reliability.

Background

              During program execution, processor performance can be improved by having critical or frequently used data or code consistently available from a low-latency cache instead of system memory. If this code or data is brought into the processor’s cache, the code or data is not guaranteed to remain in cache unless access is locked by a mechanism that prevents eviction when cache resources are filled. This procedure is termed cache-line locking.

              A program can contain several cache-locked blocks of code or data that physically map to the same set or sets in the cache. A required lock for a cacheline may not be able to be granted by the cache due to the limited ways for each cache set.

General description

              The disclosed method classifies the residency of a line in the cache at several different levels so that a program can prioritize the critical blocks to be locked. Less critical blocks, such as those with lower priority residency, are replaced in the cache before the more critical blocks, such as those with higher priority residency.

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to providing a priority field to the cache access request
•             Improved performance due to preventing a long latency for a fetch from memory because the data or code is available from the cache

•             Improved reliability due to preventing a request from replacing a cacheline containing a higher priority field

•             Improved reliability due to ensuring the most critical data/code are assured residency in the cache regardless of the cache organization or the order in which the blocks are fetched into the cache

Detailed description

              The disclosed method adds a priority field to the cache access request. The priority field is stored with the cacheline when a request causes a line to fill the cache. This field contains as many bit...