On Mon, 2008-11-24 at 21:41 -0700, David S. Ahern wrote: > > RHEL3 (which is based on the 2.4.21 kernel) gets microsecond > resolutions > by reading the TSC. Reading the TSC from within a guest is very fast > on kvm. > > RHEL4 (which is basd on the 2.6.9 kernel) allows multiple time > sources: > pmtmr (ACPI power management timer which is the default), pit, hpet > and TSC. > > The pmtmr and pit both do ioport reads to get microsecond resolutions > (see read_pmtmr and get_offset_pit, respectively). For the tsc as the > timer source gettimeofday is *very* lightweight, but time drifts very > badly and ntpd cannot acquire a sync.
Why aren't you seeing severe time drift when using RHEL3 guests with the TSC time source? -- Hollis Blanchard IBM Linux Technology Center -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
