Jan Kiszka wrote: > Gregory Haskins wrote: > >> Jan Kiszka wrote: >> >>> Hi, >>> >>> did anyone recently tried current KVM for Intel over some real-time >>> Linux? I'm seeing more than 500 us latency peaks on the host, >>> specifically during VM startup. This applies to both 2.6.29.6-rt23 and >>> Xenomai/I-pipe. For -rt, I both tried the included (patched) KVM modules >>> as well as kvm.git head with some additionally required -rt fixes. >>> Xenomai ran over a 2.6.30 kernel with my own KVM-enabler patch. >>> >>> Early instrumentation actually points to the guest exit itself: I added >>> markers right before and after the assembly part of vmx_vcpu_run, and >>> further instrumentation reports that the next host APIC tick should go >>> off right inside guest mode. But KVM leaves the switching part 500 us >>> too late in that case - as if guest exit on external IRQs was disabled. >>> >>> Will debug this further, but I'm also curious to hear other user >>> experiences. >>> >>> Jan >>> >>> >>> >> Hi Jan, >> Did you try to run with latency-tracer enabled? If not, this may >> pinpoint the source for you. >> > > I did, see above. > Ah, sorry. It wasn't clear what "instrumenation" was or if you felt it was definitively pinpointed. :P Regards, -Greg
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