Apparatus including a stall counter to bias processing element selection, and masks to allocate reservation unit entries to one or more processing elements

摘要

A method and apparatus for providing fairness in a multi-processing element environment is herein described. Mask elements are utilized to associated portions of a reservation station with each processing element, while still allowing common access to another portion of reservation station entries. Additionally, bias logic biases selection of processing elements in a pipeline away from a processing element associated with a blocking stall to provide fair utilization of the pipeline.

主权项

1. An apparatus comprising:
an execution unit to execute a plurality of instructions; a reservation unit coupled to the execution unit, the reservation unit to hold the plurality of instructions for scheduling and to hold instruction information associated with the plurality of instructions in a plurality of reservation entries, wherein the instruction information is to include dependency information and scheduling information, wherein the dependency information is to indicate that a first instruction depends from a second instruction, and wherein the scheduling information is to indicate that the first instruction should not be scheduled for execution until after the second instruction; a first storage element to include a first mask field associated with a first number of reservation entries of the plurality of reservation entries, the first mask field, when holding a first value, to indicate the first number of reservation entries are associated with a first processing element; a second storage element to include a second mask field associated with the first number of reservation entries, wherein:
when the first mask field holds the first value and the second mask field holds the first value, the first number of reservation entries are associated with the first processing element and a second processing element,when the first mask field holds the first value and the second mask field holds a second value, the first number of reservation entries are associated with the first processing element and not with the second processing element,when the first mask field holds the second value and the second mask field holds the second value, the first number of reservation entries are not associated with the first processing element and are not associated with the second processing element, andwhen the first mask field holds the second value and the second mask field holds the first value, the first number of reservation entries are associated with the second processing element and not with the first processing element; and a counter to be updated upon encountering a stall associated with either of the first and second processing elements, the counter to update in a first direction during each cycle that the stall exists, wherein during the stall a resource field is set to indicate that the processing element that is not experiencing the stall is to be selected over the processing element that is experiencing the stall, and wherein upon an exit from the stall the counter is to update in a second, opposite direction and the resource field is to be set to indicate that the processing element that had experienced the stall is to be selected over the processing element that had not experienced the stall wherein when the counter is reset to a default condition normal processing element selection is resumed.