On Fri, 13 Aug 2004, Andrew Gallatin wrote: > > I have a system where the TSC timecounter is quite a bit more accurate > (or perhaps its just much cheaper) than the ACPI timecounter. This is a > single CPU, HTT system running an SMP kernel. > > A simple program which calls gettimeofday() in a tight loop, looking > for the microseconds to change sees ~998,000 microsecond updates/sec > with kern.timecounter.hardware=TSC, and 28,500 updates/sec with ACPI-safe. > > 1) Is it safe to switch to TSC? If you like your ticks bouncing around; you'll get different values depending on which CPU you read. > 2) If yes, would it be safe to switch to TSC if this was a real > SMP system with multiple physical cpus? TSC in a single-package HTT situation would be interesting to research, if it is shared across the pipelines. -- Doug White | FreeBSD: The Power to Serve dwhite_at_gumbysoft.com | www.FreeBSD.orgReceived on Fri Aug 13 2004 - 15:38:30 UTC
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