(First, I have to admit I'm not a timekeeping expert ...) With TimeSync version 4 protocol support we started updating system time continuously through the whole lifetime of Hyper-V guests. Every 5 seconds there is a time sample from the host which triggers do_settimeofday[64](). While the time from the host is very accurate such adjustments may cause issues: - Time is jumping forward and backward, some applications may misbehave. - In case an NTP client is run in parallel things may go south, e.g. when an NTP client tries to adjust tick/frequency with ADJ_TICK/ADJ_FREQUENCY the Hyper-V module will not see this changes and time will oscillate and never converge. - Systemd starts annoying you by printing "Time has been changed" every 5 seconds to the system log. With this series I suggest to use do_adjtimex() to adjust time. My tests show that such method gives equally good time convergence but avoids all the drawbacks described above. Vitaly Kuznetsov (4): timekeeping: export do_adjtimex() to modules hv_util: switch to using timespec64 hv_util: use do_adjtimex() to update system time hv_util: improve time adjustment accuracy by disabling interrupts drivers/hv/hv_util.c | 33 +++++++++++++++++++++++++++++---- kernel/time/timekeeping.c | 1 + 2 files changed, 30 insertions(+), 4 deletions(-) -- 2.9.3 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
