* Dor Laor <[EMAIL PROTECTED]> wrote:
> Hi Ingo, Thomas,
>
> In the latest kernel (2.6.24-rc3) I noticed a drastic performance
> decrease for KVM networking. The reason is many vmexit (exit reason is
> cpuid instruction) caused by calls to gettimeofday that uses tsc
> sourceclock. read_tsc calls get_cycles_sync which might call cpuid in
> order to serialize the cpu.
>
> Can you explain why the cpu needs to be serialized for every gettime
> call? Do we need to be that accurate? (It will also slightly improve
> physical hosts). I believe you have a reason and the answer is yes. In
> that case can you replace the serializing instruction with an
> instruction that does not trigger vmexit? Maybe use 'ltr' for example?
hm, where exactly does it call CPUID?
Ingo
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