1. A method comprising: receiving a host memory subsystem on a host hardware platform, the host memory subsystem including a memory device; for each of multiple different settings for multiple different I/O (input/output) circuit parameters for a target I/O performance characteristic for I/O with the memory device, setting a value for each I/O circuit parameter; generating test traffic with a test engine embedded in the host memory subsystem to stress test the memory device; and measuring an operating margin for the I/O performance characteristic; executing a search function to determine values for each I/O circuit parameter at which the operating margin meets a minimum threshold, and performance of at least one of the I/O circuit parameters is increased; and setting runtime values for the I/O circuit parameters based on the search function.