What is HPET ?

HPET stands for “High Precision Event Timer” – HPETs were introduced in 2005 to replace the read-time stamp counter (RDTSC) on x86 computers. HPETs run at 10 or 100Mhz providing a time “tick” of either 100 or 10ns respectively.

The HPET was introduced to serve multimedia applications with a high rate clocking mechanism to ensure smooth playback of video. Linux kernels can reference HPET time through various system calls. Lacking a precision time source, developers in finance resort to using HPET to time system events, but HPET shortcomings have become problematic as applications which demand real world time now span several cores on different processors. Although HPETs provide a fine grained tick time they suffer from serious
failings when used for system performance timing in financial applications as they were primarily designed for multimedia.

HPETs are largely only accurate on a “per core” basis due to CPU bus synchronization issues. Developers wishing to access this timing directly are constrained with either pinning all threads within a

process to a single core, or worse yet binding multiple processes with multiple threads to a single core to achieve equitably accurate clock times. Moreover, widely varied and constantly changing HPET configurations force development teams to constantly struggle to maintain instrumentation within applications, distracting them from the core business logic.