International Business Machines Corporation

Winston Herring

Gregory William Alexander

Timothy Carl Bronson

Jason D Kohl

Christian Jacobi

Tu-An T Nguyen

Matthias Klein

Akash V Giri

Embodiments are for using a decentralized hot cache line tracking fairness mechanism. In response to receiving an incoming request to access a cache line, a determination is made to grant access to the cache line based on a requested state and a serviced state used for maintaining the cache line, a structure comprising the requested and serviced states. In response to the determination to grant access to the cache line, the requested state and the serviced state are transferred along with data of the cache line.

Decentralized hot cache line tracking fairness mechanism

A node of the computing environment obtains an exclusive fetch request of a cache line shared by, at least, the node and a manager node of the computing environment. The exclusive fetch request includes a state indication regarding processing of the exclusive fetch request by the manager node. The node processes the exclusive fetch request, based on the state indication included with the exclusive fetch request regarding processing of the exclusive fetch request by the manager node.

Invalidity protection for shared cache lines

A method for managing designated authority status in a cache line includes identifying an initial designated authority (DA) member cache for a cache line, transferring DA status from the initial DA member cache to a new DA member cache, determining whether the new DA member cache is active, indicating a final state of the initial DA cache responsive to determining that the new DA member cache is active, and overriding a DA state in a cache control structure in a directory. A method for managing cache accesses during a designated authority transfer includes receiving a designated authority (DA) status transfer request, receiving an indication that a first cache will invalidate its copy of the cache line, allowing a second cache to assume DA status for the cache line, and denying access to the first cache's copy of the cache line until invalidation by the first cache is complete.

Final cache directory state indication

A primary controller has authority of a cache line associated with a fetch and manages a second cache line request from a different and non-associated secondary requesting entity. A secondary controller, associated with the secondary requesting entity, is granted authority of the cache line and further manages multiple subsequent simultaneous or overlapping requests for the cache line from different non-associated subsequent requesting entities by maintaining authority of the cache line, by granting read-only access to the cache line to respective subsequent controllers, each associated with a different subsequent requesting entity, and by passing a non-authority token to each of the respective subsequent controllers.

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Winston Herring