Data storage system with performance-based distribution of i/o requests to processing cores

A data storage system comprising secondary storage devices, front-end ports for coupling to a network to receive host I/O requests, processing circuitry including a plurality of processing cores, and back-end ports coupling the processing circuitry to the secondary storage devices, the processing circuitry being configured and operative to execute operating software to perform a method of assigning I/O requests to the processing cores, the method including:

• in a first operating mode, assigning the I/O requests to the cores based on port affinity while maintaining a current I/O completion count, and regularly performing a first test-and-switch operation including (i) for a sample interval, temporarily assigning the I/O requests to the cores based on core availability while obtaining a sample I/O completion count, (ii) comparing the first sample I/O completion count to the current I/O completion count, and (iii) based on the sample I/O completion count being greater than the current I/O completion count, switching to a second operating mode;
• and
• in the second operating mode, assigning the I/O requests to the cores based on core availability while maintaining the current I/O completion count, and regularly performing a second test-and-switch operation including (i) for a sample interval, temporarily assigning the I/O requests to the cores based on port affinity while obtaining the sample I/O completion count, (ii) comparing the sample I/O completion count to the current I/O completion count, and (iii) based on the sample I/O completion count being greater than the current I/O completion count, switching to the first operating mode.