Messages in this thread | | | Subject | RE: Dual core Athlons and unsynced TSCs | From | john stultz <> | Date | Fri, 13 Jan 2006 17:39:33 -0800 |
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On Fri, 2006-01-13 at 20:27 -0500, Lee Revell wrote: > On Fri, 2006-01-13 at 17:23 -0800, john stultz wrote: > > On Fri, 2006-01-13 at 20:14 -0500, Lee Revell wrote: > > > On Fri, 2006-01-13 at 20:10 -0500, Steven Rostedt wrote: > > > > > > > > Thanks, I'll add that to my list of tests too. > > > > > > > > Oh and 2.6.15 passed as well (with clock=pmtmr) > > > > > > It really seems like it would fail if you gave it enough time due to the > > > rdtsc in monotonic_clock()... > > > > Currently monotonic_clock()is only used by the hangcheck-timer, and is > > not used by gettimeofday/clock_gettime (even w/ CLOCK_MONOTONIC). > > > > So there may still be an issue there w/ the hangcheck-timer(for x86-64, > > on i386 the acpi pm timer can be used for monotonic_clock), but its > > doesn't affect the time related userland interfaces. > > OK so the last question is how do we make sure the kernel uses the > clock=pmtmr behavior by default on those machines?
This is as I understand it:
With 2.6.15 on x86-64: If available, alternate timesources (HPET, ACPI PM) will be used if available on AMD SMP systems. (clock= is i386 only)
With 2.6.15 on i386: If CONFIG_X86_PM_TIMER is enabled, and available it is the preferred clocksource over the TSC. Some distros have changed this priority causing the TSC to be preferred. In these cases clock=pmtmr is needed.
How's that? -john
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