On Fri, 17 Aug 2007, Mathieu Desnoyers wrote: > > The cpu will definitely not be idle during these measurements and no > > frequency scaling is active. > > The problem is that if the cpu is idle _before_ the measurements, the > frequency will change differently from one cpu to another. Therefore, > the cycle counters may have large offsets when you start your tests. So, > if get_cycles() is executed on different CPUs (thread being migrated) > between the beginning and the end of the test, the results would be > skewed.
TSC measurements as done by this patch are associated with cpus. The skew is irrelevant. Development of this patchset was done on a system whose TSC are never synchronized. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
