linux-kernel - Re: system call time increase when turning on CONFIG

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Date:	Fri, 02 Mar 2007 23:00:59 -0800
From:	Zachary Amsden <zach@...are.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	tim.c.chen@...ux.intel.com, linux-kernel@...r.kernel.org,
	Virtualization Mailing List <virtualization@...ts.osdl.org>
Subject: Re: system call time increase when turning on CONFIG_PARAVIRT

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
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