Date: Fri, 13 Aug 2004 12:49:15 -0400 (EDT) From: Andrew Gallatin <gallatin@cs.duke.edu> To: freebsd-current@freebsd.org Subject: Is the TSC timecounter safe on SMP system? Message-ID: <16668.61707.474283.639200@grasshopper.cs.duke.edu>
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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? 2) If yes, would it be safe to switch to TSC if this was a real SMP system with multiple physical cpus? Thanks, Drew
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