Re: Dual core Athlons and unsynced TSCs

thockin
2006-01-13T18:06:41Z

On Fri, Jan 13, 2006 at 12:58:36PM -0500, Lee Revell wrote:
> > If your BIOS has an ACPI "HPET" table, then the kernel can use the HPET
> > timer instead. It doesn't solve the problem for apps or other kernel bits
> > that use rdtsc directly, but there are other fixes for that floating
> > around which will hopefully get consideration when they're mature.
>
> The apps can be converted to use clock_gettime(), but that does not help
> if the kernel can't keep reasonable time on these machines.

Some apps/users need higher resolution and lower overhead that only rdtsc
can offer currently.

> But if we just use "clock=pmtmr" by default on these machines the TSC is
> not a problem right?

I never tried it with pmtimer, we had HPET available. Empirically TSC did
not work (and we had a simple test case to show how bad it could get).
HPET made that go away for users of gettimeofday().

We're exploring rdtsc-compatible solutions.