system call time increase when turning on CONFIG_PARAVIRT

[Zachary Amsden]

Jeremy Fitzhardinge wrote:
> Tim Chen wrote:
>   
>> I also hope that the performance can be recovered as this option could
>> enabled in distributions' kernels in future.
>>     
>
> Yes, the intent is that running a CONFIG_PARAVIRT kernel on native
> hardware will have negligible performance hit compared to running a
> non-paravirt kernel.
>   

We can validate that claim entirely.  The way we are proceeding, the 
native code will be inlined or direct called as much as possible.  With 
the VMI-Linux code we had earlier, this mostly created <3% overhead for 
microbenchmarks (and in some cases, we actually won over the unmodified 
native code).  For macro-benchmarks, with real-world workloads, this 
reduced to immeasurable noise, never off by more than +/- 0.5% IIRC.

I believe all of this is totally achievable.  We have the technology.  
We can rebuild it.

Zach