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Method and System for Allowing Access to Data Locked by a State Machine for Eviction in a Multilevel Write Back Cache

IP.com Disclosure Number: IPCOM000237412D
Publication Date: 2014-Jun-17
Document File: 2 page(s) / 30K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method and system is disclosed for allowing one or more of a processor and a next level cache to read one or more lines locked by a state machine for eviction from a multilevel write back cache.

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Method and System for Allowing Access to Data Locked by a State Machine for Eviction in a Multilevel Write Back Cache

In the current art, when a cache entry has been selected for eviction from the cache to

make space for another cache line, the entry is locked by a state machine within the cache controller. The state machine is responsible for removing the line from the cache and storing it back to main memory or the next level cache.

While the state machine is processing the cache eviction, it is possible for another processor or a next level cache to simultaneously attempt to read the cache entry that is being evicted. In the case of another processor request, the processor must wait for the cache eviction to complete before the processor attempts to re-access the evicted line and proceed as a cache miss. In the case of a request from the next level cache, care must be taken to avoid a coherency deadlock. One solution for this may be to allow the cache eviction to complete before processing the request from the next level cache, but such a solution is likely to delay the processing of said request. Another

solution may be to require the eviction to first check with the next level cache before proceeding, but such a solution is likely to slow-down the eviction of the cache line.

Disclosed is a method and system for allowing requests from at least one of a processor and a next level cache to access data that has been locked by a state machine processing a cache eviction.

In accordance with the method and system, when a cache entry is selected...