Messages in this thread | | | Date | Fri, 24 Jun 2005 13:56:12 -0700 | From | "Martin J. Bligh" <> | Subject | Re: 2.6.12-mm1 boot failure on NUMA box. |
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--On Friday, June 24, 2005 21:52:48 +0200 Ingo Molnar <mingo@elte.hu> wrote:
> > * Martin J. Bligh <mbligh@mbligh.org> wrote: > >> > - /* >> > - * In the NUMA case we dont use the TSC as they are not >> > - * synchronized across all CPUs. >> > - */ >> > -#ifndef CONFIG_NUMA >> > - if (!use_tsc) >> > -#endif >> > + if (!cpu_has_tsc) >> > /* no locking but a rare wrong value is not a big deal */ >> > return jiffies_64 * (1000000000 / HZ); >> >> Humpf. That does look dangerous on a NUMA-Q. The TSCs aren't synced, >> and we can't use them .... have to use PIT, whether the CPUs have TSC >> or not. > > is the only problem the unsyncedness? That should be fine as far as the > scheduler is concerned. (we compensate for per-CPU drifts)
Well, I think so. But I don't see how you're going to compensate for large-scale unsynced-ness safely. I've always completely avoided the TSC altogether on NUMA-Q ... would prefer to keep it that way. We got lots of wierd random crashes, panics, hangs, and -ve time offsets returned from userspace time commands last time I tried it.
M.
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