Hyper-Threading Aware Process Scheduling Heuristics

Intel Corporation's "Hyper-Threading Technology" is the first commercial implementation of simultaneous multithreading. Hyper-Threading allows a single physical processor to execute two heavyweight threads (processes) at the same time, dynamically sharing processor resources. This dynamic sharing of resources, particularly caches, causes a wide variety of inter-thread behaviour. Threads competing for the same resource can experience a low combined throughput.

Hyper-Threads are abstracted by the hardware as logical processors. Current generation operating systems are aware of the logical-physical processor hierarchy and are able to perform simple load-balancing. However, the particular resource requirements of the individual threads are not taken into account and sub-optimal schedules can arise and remain undetected.

We present a method to incorporate knowledge of per-thread Hyper-Threading performance into a commodity scheduler through the use of hardware performance counters and the modification of dynamic priority.