Performance-based reallocating of logical processing units to sockets of a computer system

A multiprocessor computer system facility is provided for selectively reallocating a logical processing unit. The logical processing unit is one logical processing unit of multiple logical processing units backed by a socket of a plurality of sockets of a multiprocessor computer system. The selectively reallocating includes: monitoring, during execution of program code, a performance metric of a hardware resource of the socket, the hardware resource being shared by the multiple logical processing units; and reassigning the logical processing unit, based on the monitoring, to a different socket of the plurality of sockets of the multiprocessor computer system to, in part, improve the performance metric of the hardware resource of the socket. The reassigning includes reassigning the logical processing unit based on the monitoring determining that a differential between a resource utilization rate of the socket and a resource utilization rate of the different socket exceeds a set threshold.