Messages in this thread | | | Date | Fri, 21 Oct 2005 02:03:13 -0400 (EDT) | From | Steven Rostedt <> | Subject | Re: Ktimer / -rt9 (+custom) monotonic_clock going backwards. |
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On Thu, 20 Oct 2005, Ingo Molnar wrote:
> > * john stultz <johnstul@us.ibm.com> wrote: > > > > > John, would this cause any problems to keep cycle_t at s64? > > > > > > I mean at u64. > > > > Performance would be the only concern. It had been a u64 before I > > started optimizing the code a bit. > > no, this is really a bad optimization that causes unrobustness. > Correctness and robustness comes first. It is so easy to cause a > 500-1000msec delay in the kernel, due to a bad driver or anything. The > timekeeping code should not break like that. >
FYI,
With rc4-rt13 and changing cycle_t to u64, my machine ran all night without one backward step. Since it use to show up after a couple of hours, I would say that this is the fix.
John, Do you want me to take a crack at changing the periodic_hook into using the ktimer code? I understand Ingo's kernel much more than you, but you definitely understand the timing code better than I.
Cheers,
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