Issue queue with dynamic shifting between ports

A system comprising:

• an issue queue of a processor, the issue queue comprising a first shared port associated with a plurality of instructions of a first type and a second shared port associated with a plurality of instructions of a second type, and the first and second shared ports are configurable to dispatch at least three types of instructions;
• and
• a dispatch unit of the processor operable to perform a plurality of operations comprising:
• monitoring a number of instructions of the first type dispatched to the first shared port of the issue queue using a port first instruction type counter;
• determining whether the number of instructions of the first type dispatched to the first shared port exceeds a port selection threshold by comparing a value of the port first instruction type counter to the port selection threshold based on a most recent number of dispatched instructions over a predetermined number of instructions;
• dispatching an instruction of a third type to the second shared port of the issue queue based on determining that the number of instructions of the first type dispatched to the first shared port exceeds the port selection threshold, wherein the value of the port first instruction type counter is greater than the port selection threshold;
• dispatching the instruction of the third type to the first shared port of the issue queue based on determining that the number of instructions of the first type dispatched to the first shared port does not exceed the port selection threshold, wherein the value of the port first instruction type counter is less than the port selection threshold;
• monitoring for a plurality of port selection conflicts between different types of instructions at the first shared port and the second shared port of the issue queue;
• and
• adjusting the port selection threshold based on determining that the port selection conflicts exceed a conflict threshold to switch instruction type assignments between the first shared port and the second shared port, wherein adjusting the port selection threshold comprises increasing the port selection threshold based on the number of conflicts at the first shared port per period of time that exceeds the conflict threshold, and decreasing the port selection threshold based on the number of conflicts at the second shared port per period of time that exceeds the conflict threshold.

A computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to perform operations comprising:

• monitoring a number of instructions of a first type dispatched to a first shared port of an issue queue using a port first instruction type counter, wherein the issue queue comprises at least two shared ports to dispatch at least three types of instructions;
• determining whether the number of instructions of the first type dispatched to the first shared port exceeds a port selection threshold by comparing a value of the port first instruction type counter to the port selection threshold based on a most recent number of dispatched instructions over a predetermined number of instructions;
• dispatching an instruction of a third type to a second shared port of the issue queue associated with a plurality of instructions of a second type based on determining that the number of instructions of the first type dispatched to the first shared port exceeds the port selection threshold, wherein the value of the port first instruction type counter is greater than the port selection threshold;
• dispatching the instruction of the third type to the first shared port of the issue queue associated with a plurality of instructions of the first type based on determining that the number of instructions of the first type dispatched to the first shared port does not exceed the port selection threshold, wherein the value of the port first instruction type counter is less than the port selection threshold;
• monitoring for a plurality of port selection conflicts between different types of instructions at the first shared port and the second shared port of the issue queue;
• and
• adjusting the port selection threshold based on determining that the port selection conflicts exceed a conflict threshold to switch instruction type assignments between the first shared port and the second shared port, wherein adjusting the port selection threshold comprises increasing the port selection threshold based on the number of conflicts at the first shared port per period of time that exceeds the conflict threshold, and decreasing the port selection threshold based on the number of conflicts at the second shared port per period of time that exceeds the conflict threshold.