Neel Natu wrote: > Hi Paul, > > On Fri, Apr 10, 2015 at 10:35 AM, Paul Vixie <p...@redbarn.org> wrote: >> ... >> >> can we make TSC-low the default? >> > > The choice of using the TSC is not without issues: > > - As rstone@ points out the TSCs need to be synchronized across physical cpus.
ok, then the reason i'm not seeing this is i have a single 6-core CPU. (ntpd would complain about clocks going backward.) > - Depending on system load the guest's estimate of the TSC frequency > might be way off the mark. i see what you mean. > So, in a way the HPET or the ACPI time counters are better since both > the host and guest agree on the frequency. But it seems there is > either an issue with the emulation or an artifact due to the > guest-to-host round trip time. to be fair, some of my bhyve's ran fast (so, positive adjustments by ntpd), some ran slow (negative adjustments). i did not try every possible timecounter hardware; TSC-low fixed it, so i stopped. > I have been doing experiments but don't have anything conclusive yet. thanks for looking into it. paravirtualization (kvm-clock or some equivalent) seems desirable. -- Paul Vixie _______________________________________________ firstname.lastname@example.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-virtualization To unsubscribe, send any mail to "freebsd-virtualization-unsubscr...@freebsd.org"