1. A method for use in managing system I/O load, the method comprising: when a background operation is available to be executed on a processor core, determining whether a credit value associated with the processor core satisfies a memory use criterion; executing the background operation on the processor core when the credit value associated with the processor core satisfies the memory use criterion, the background operation having a memory use requirement; modifying the credit value associated with the processor core by an amount corresponding to the memory use requirement; detecting that memory is required for operations other than background operations; and in response to said detection, reducing a level of replenishments of credits for the processor core in order to allow more memory for the operations other than the background operations, wherein before the reduction the level of replenishment was set to replenish the credits to the credit value.