On Wed, Jun 01, 2022, Vitaly Kuznetsov wrote: > hyperv_clock doesn't always give a stable test result, especially with > AMD CPUs. The test compares Hyper-V MSR clocksource (acquired either > with rdmsr() from within the guest or KVM_GET_MSRS from the host) > against rdtsc(). To increase the accuracy, increase the measured delay > (done with nop loop) by two orders of magnitude and take the mean rdtsc() > value before and after rdmsr()/KVM_GET_MSRS. Rather than "fixing" the test by reducing the impact of noise, can we first try to reduce the noise itself? E.g. pin the test to a single CPU, redo the measurement if the test is interrupted (/proc/interrupts?), etc... Bonus points if that can be implemented as a helper or pair of helpers so that other tests that want to measure latency/time don't need to reinvent the wheel.
