Jim Houston <jim.houston@attbi.com> writes:
> I believe that this is the result of lost ticks. It has gotten much
> easier to lose a tick since HZ was changed to 1000. When the timer
> interrupt is delayed, the other processors will continue to keep reasonable
> time (based on the TSC), but when the timer interrupt eventually happens,
> it will add one tick's worth of nanoseconds to xtime.tv_nsec and set
> last_tsc_low to the current tsc value. The other processors now base
> their time on this new last_tsc_low and will see time go backwards.
It could be detected by keeping a per cpu last_tsc.
Best would be to use a global timer like HPET, but it's not available
everywhere and much slower than rdtsc too.
-Andi
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This archive was generated by hypermail 2b29 : Sat Nov 23 2002 - 22:00:27 EST