Re: [patch 04/17] Add pagetable accessors to pack and unpack pagetable entries

Andi Kleen
2007-04-04T11:47:56Z

On Wednesday 04 April 2007 11:25:57 Jeremy Fitzhardinge wrote:
> Andi Kleen wrote:
> > What do the benchmarks say with CONFIG_PARAVIRT on native hardware
> > compared to !CONFIG_PARAVIRT. e.g. does lmbench suffer?
>
> Barely. There's a slight hit for not using patching, and patching is
> almost identical to native performance. The most noticeable difference
> is in the null syscall microbenchmark, but once you get to complex
> things the difference is in the noise.

Why is there a difference for null syscall? I had assumed we patched all the
fast path cases relevant there. Do you have an idea where it comes from?

-Andi