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PROVISION OF INTERNAL CACHE STATUS FOR EXTERNAL CACHE MANAGEMENT

IP.com Disclosure Number: IPCOM000005610D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2001-Oct-19
Document File: 1 page(s) / 56K

Publishing Venue

Motorola

Related People

Bill Moyer: AUTHOR [+2]

Abstract

Performance of a cache memory may be improved by allowing cache entries for multiple processes to reside in the cache concurrently. When a context switch occurs, the cache does not need to be automatically flushed of all entries, If the cache is large enough, upon returning to a process, cache entries for that process may still be resident. By allowing cache entries to remain in the cache across context switches, the hit rate of the cache increases.

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MOlOROLA Technical Developments Volume 6 October 1986

PROVISION OF INTERNAL CACHE STATUS FOR EXTERNAL CACHE MANAGEMENT

by Bill Moyer and Brad Cohen

   Performance of a cache memory may be improved by allowing cache entries for multiple processes to reside in the cache concurrently. When a context switch occurs, the cache does not need to be automatically flushed of all entries, If the cache is large enough, upon returning to a process, cache entries for that process may still be resident. By allowing cache entries to remain in the cache across context switches, the hit rate of the cache increases.

   To allow entries for multiple tasks to be resident in a cache, a method of identifying these tasks must be provided. The MC68851 PMMU provides support for automatically identifying a task based on its translation path, and will assign a unique "task alias" identifier to each task, relieving the operating system software of the burden. The PMMU identifies a task based on its root pointer value, and contains a cache of root pointer values for up to eight tasks. The root pointer points to the root of the translation tree used for a task. In its simplest form, the task alias assigned to a process is the index into the root pointer cache where the root pointer for that particular task is found. If no root pointer is found in the root pointer cache, a task alias is reused, and the translation entries associated with the old task are flushed from the translation cache. This task...