Snoop filter for cache coherency in a data processing system

Abstract

A data processing system, having two or more of processors that access a shared data resource, and method of operation thereof. Data stored in a local cache is marked as being in a UniqueDirty, SharedDirty, UniqueClean, SharedClean or Invalid state. A snoop filter monitors access by the processors to the shared data resource, and includes snoop filter control logic and a snoop filter cache configured to maintain cache coherency. The snoop filter cache does not identify any local cache that stores the block of data in a SharedDirty state, resulting in a smaller snoop filter cache size and simple snoop control logic. The data processing system by be defined by instructions of a Hardware Description Language.

Description

technical field [0001] The present disclosure relates to data processing systems, and more particularly to snoop filters for cache coherency in data processing systems. Background technique [0002] A data processing system, such as a system on a chip (SoC), may contain multiple processor cores, multiple data caches, and shared data resources. For example, in a shared memory system, each processor core can read and write to a single shared address space. Cache coherency is an issue in any system that includes one or more caches and where more than one device shares data in a single cache. There are two potential problems with systems that include multiple caches. First, the memory can be updated (by another device) after the cached device has fetched the copy. At this point, the data in the cache is expired or invalid, and no longer contains the latest data. Second, systems that include write-back caching must handle situations in which a device writes to a copy of the l...

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Problems solved by technology

At this point, the data in the cache is expired or invalid, and no longer contains the latest data

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