Queue resource tracking in a multiprocessor system

Abstract

A multiprocessor computer system including a set of processors where each processor in the set includes an execution unit for issuing operations and a processor queue suitable for queuing previously issued and still pending operations. The multiprocessor further includes means for forwarding operations issued by the processor to the processor queue and to an operation block queue of a memory subsystem that is connected to the multiprocessor. The depth of (i.e., the number of entries in) the operation block queue matches the depth of the processor queue. The processor queue, when full, inhibits the processor from issuing additional operations. In this manner, an operation issued by the processor is guaranteed an available entry in the operation block queue of the memory subsystem thereby eliminating the need for operation retry circuitry and protocols such as handshaking. Preferably, each processor queue includes a processor load queue and a processor store queue and the operation block queue includes a load queue and a store queue. In this embodiment, the depth of each of the processor load and store queues matches the depth of the operation block load and store queues respectively. In the preferred embodiment, the operation block is comprised of a load miss block that includes the operation block load queue and a store miss block that includes the operation block store queue. Still further preferably, the operation block store queue includes a set of store queues corresponding to the set of processors and the operation block load queue includes a set of load queues corresponding to the set of processors. Each queue entry preferably includes state information indicative of the status of the corresponding entry.