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Demote instruction for relinquishing cache line ownership

  • US 9,311,238 B2
  • Filed: 06/18/2014
  • Issued: 04/12/2016
  • Est. Priority Date: 12/12/2007
  • Status: Active Grant
First Claim
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1. A method for relinquishing cache ownership of a cache line, the method comprising executing, by a selected processor of a multi-processor system, a demote instruction, the demote instruction specifying a logical address, the multi-processor system comprising a multi-cache system and a cache coherency ownership scheme for providing any one of shared ownership and exclusive ownership of a cache line to caches of the multi-processor system, an exclusively owned cache line configured to be accessible, by a processor, in only one cache of the multi-cache system, the only one cache having the exclusively owned cache line, a shared ownership cache line configured to be accessible, by processors, in a plurality of caches of the multi-cache system, the plurality of caches having the shared ownership cache line, the executing the demote instruction performing a method comprising:

  • based on the specified logical address, determining whether a cache line of the cache system, is exclusively owned by a selected cache of the selected processor;

    based on determining that the cache line is exclusively owned by the selected cache of the selected processor, relinquishing, by the selected cache, exclusive ownership of the cache line; and

    based on executing the demote instruction, the selected processor completes all pending stores before relinquishing the exclusive ownership of the cache line, wherein the relinquishing the exclusive ownership of the cache line comprises setting the ownership of the cache line of the selected cache to any one of shared ownership or read-only allowing a processor of the multiprocessor system to immediately be given exclusive ownership to that cache line without waiting on any processor'"'"'s explicit cross invalidate acknowledgement, and wherein execution of the demote instruction performs no architectural update.

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