On 07/09/11 03:57, Maurice Janssen wrote: > Hi, > > Is it possible to somehow force a program to run on a single CPU in an > SMP system? > The reason I ask that on some SMP-capable architectures, I'm having some > problems with ntpd. On hppa and sgi, the clock won't sync because ntpd > sees replies with negative delay: > > Jul 9 08:58:19 hppa ntpd[21406]: reply from 192.168.4.12: negative > delay -0.854615s, next query 3120s > > (reported as PR6592) > > If I run the bsd.sp kernel, the negative delays are gone and ntpd syncs > without any problem. I was wondering if the problem would occur if I > could limit ntpd to a single CPU. Diving into the code is way beyond my > skills, so I was hoping that there is a utility like nice to achieve this. > > Thanks, > Maurice
Things aren't that simple. Time is an illusion. Lunch time, doubly so (obligatory Hitchhiker's quote) Time on computers is complicated, doubly so on a multiprocessor system. ntpd isn't your problem, it's time on the SMP system. Fiddling with processor affinity (trying to attach particular tasks to particular CPUs) wouldn't help if you could (and you can't). Is time really drifting (consistently increasing error in one direction) on these systems? Or is it just "jittering" around proper time? If it is really drifting, you should probably put in a problem report on this. Nick.
