Computer system having cache subsystem performing demote requests

摘要

Computer system having cache subsystem wherein demote requests are performed by the cache subsystem. Software indicates to hardware of a processing system that its storage modification to a particular cache line is done, and will not be doing any modification for the time being. With this indication, the processor actively releases its exclusive ownership by updating its line ownership from exclusive to read-only (or shared) in its own cache directory and in the storage controller (SC). By actively giving up the exclusive rights, another processor can immediately be given exclusive ownership to that said cache line without waiting on any processor's explicit cross invalidate acknowledgement. This invention also describes the hardware design needed to provide this support.

主权项

1. A computer system comprising one or more microprocessor cores each having an instruction dispatch unit, a fixed point unit and a load store unit, and a cache subsystem, the computer system configured to perform a method comprising:
executing, by a selected microprocessor core of the computer system, a demote instruction, the demote instruction specifying a cache line of the cache subsystem, wherein the selected microprocessor core has exclusive ownership of the specified cache line; and based on the executing the demote instruction, relinquishing exclusive ownership of the cache line owned by said selected microprocessor core, the cache line specified by the demote instruction, the relinquishing causing the cache line of the cache subsystem to be any one of exclusive-to-no-one, shared or read-only.