Hello, (2012/08/25 0:00), Marcelo Tosatti wrote: <snip>
kvmclock driver has access to the ntpd corrected frequency of the host, but: 1) kvmclock time as reported to the guest uses the TSC as an offset in addition to the host monotonic clock, TSC is susceptible to frequency variations. The guest has its own timekeeping (it accumulates time from kvmclock, at every timer interrupt). The algorithm is not perfect, and its suspectible to small variations. These add up over time. 2) Corrections to UTC, such as leap seconds, are not reflected to the host monotonic clock. NTP algorithm in the guest is responsible for synchronization to UTC.
I see, I understood the pitfalls of the guest only syncing to kvmclock, and now NTP on the guest seems simple and reasonable for me. Thank you again for your detailed explanation. Sincerely, --- Aritoki TAKADA aritoki.takada.jt@xxxxxxxxxxx Hitachi, Ltd., Yokohama Research Laboratory -- 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
