Deterministic scheduling with local APIC

Jacob Gorm Hansen jg at
Mon Jan 13 15:33:28 CET 2003

hi again,

[OT: First of all a great thanks to everyone at TU Dresden for the
interesting discussions and pleasant company during our visit last

Following a discussion with Jan Glauber Friday evening on the HP
Somersault API, which does failover by making sure processes on a
standby machine receive the exact same inputs as those on the master
machine, I wondered if anyone knows if the PentiumII local APIC is
precise enough that you can do completely deterministic scheduling, say,
in Fiasco?

It seems to me that one could implement an OS-level failover system by
wrapping the OS in an I/O environment (like NomadBIOS ;-)) which would
somehow ensure that the exact same input was received at both the master
and the slave hosts, provided that the scheduling performed by the
kernel scheduler could be performed with clockcycle precision (otherwise
race conditions would allow things to get out of sync).

Does anyone have an opinion as to whether or not this might be possible
using current Intel hardware?



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