2016-02-24 09:35-0800, Peter Hornyack: > On Tue, Feb 23, 2016 at 7:57 PM, Marcelo Tosatti <mtosatti@xxxxxxxxxx> wrote: >> On Tue, Feb 23, 2016 at 06:31:59PM -0800, Owen Hofmann wrote: >>> Regardless of my opinion, I think that a clear statement of the design >>> goals for kvm-clock (and kvm's implementation of the reference TSC >>> page) would be valuable. >> >> Documentation/virtual/kvm/timekeeping.txt >> > > Hi Marcelo, > > While I appreciate all of the detail in timekeeping.txt, it is not a > very good reference for what kvm-clock is or how it works. kvm-clock > is only mentioned three times in different places throughout that > document, and nowhere is there a very clear statement of what > kvm-clock is supposed to do or how it does it. > > For somebody that does not already have a deep understanding of the > core masterclock code, trying to understand how kvm-clock works is a > real challenge. I agree. Having an overview would be very helpful. Do you find anything incorrect with * kvmclock measures the flow of time. * time in kvmclock flows at the same rate as host's CLOCK_BOOTTIME. ? Maybe it would be better to say "best estimate of real time" instead of "CLOCK_BOOTTIME", so people wouldn't jump to conclusion that CLOCK_BOOTTIME has something to do with kvmclock ... Then we could mention migration (why the time becomes imprecise) and finish by explaining the TSC mechanism (that avoids a vmexit on every read) and advantages of masterclock. -- 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
