>> aren't there known issues with the tc you mentioned and SMP systems?
> Don't know - but one possibility that would fit the symptoms would be
> if there are multiple usage counters (one per cpu) and somehow the
> values are just coming from one of them, and it isn't the right one.
Hmm...have you tried a non-MP kernel? Have you tried nailing your test
down on each of the available CPUs? Have you tried running various
numbers of infinite-loop CPU-burners at the same time?
Each of those might hint at the actual problem.
Maybe ktrace could use a "migrated to a different CPU" tracepoint?
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