On 17/12/2014 18:41, Marcelo Tosatti wrote: >> > Btw. simple automatic delta tuning had worse results? > Haven't tried automatic tuning. > > So what happens on a realtime environment is this: you execute the fixed > number of instructions from interrupt handling all the way to VM-entry. > > Well, almost fixed. Fixed is the number of apic_timer_fn plus KVM > instructions. You can also execute host scheduler and timekeeping > processing. > > In practice, the length to execute that instruction sequence is a bell > shaped normal distribution around the average (the right side is > slightly higher due to host scheduler and timekeeping processing). > > You want to advance the timer by the rightmost bucket, that way you > guarantee lower possible latencies (which is the interest here). > > That said, i don't see advantage in automatic tuning for the usecase > which this targets. Yeah, the value of the parameter can be computed pretty easily from either the tracepoint or the kvm-unit-tests testcase. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
