[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] Time went backwards
> > I have been experimenting with frequency scaling on a 4 core (2 > > sockets) AMD Opteron processors. The versions of Xen I have tested > > with include xen-testing as well as xen-unstable (cs > 17042). For both > > these versions, I am using the linux 2.6.18-8 tree and have passed > > cpufreq=dom0-kernel to the xen command line. > > > > However, I get plenty of "Time went backwards" whenever I attempt to > > change frequency. Does anyone know how this can be fixed? > > > > % grep name /proc/cpuinfo | head -1 > > model name : Dual-Core AMD Opteron(tm) Processor 2216 HE > > > > powernow-k8: error - out of sync, fix 0x10 0x10, vid 0xe 0xc > > powernow-k8: error - out of sync, fix 0x10 0x2, vid 0xc 0x12 > > Presumably you have cpufreq=dom0-kernel on your Xen command > line? Apart from > that noone else has reported 'out of sync' messages from the powernow > driver. Mark may have some idea what that could be about. He's got a dual-core system, but the logical grouping of the cores doesn't match the physical grouping. Something like cores 0,1 share frequencies, but PowerNow! believes that cores 0 and 2 do. So when a frequency change on core 0 occurs, the Xen hypervisor gets alerted that cores 0 and 2 have new frequencies. This causes two errors with Xen - the HV believes core 1 has the old frequency, when it has the new frequency, and it believes core 2 has the new frequency, when it really has the old frequency. Time errors will accumulate rapidly. Niraj - Please email me privately. I have some more time to work on this issue and some new ideas on how to get information about it. Thanks! -Mark Langsdorf Operating System Research Center AMD _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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