Re: [RFC] VMX CR3 cache

Ingo Molnar
2008-01-28T17:37:08Z

* Marcelo Tosatti <marcelo-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org> wrote:

> > when i did the testing then i was able to get zero VM exits in the
> > lat_ctx hotpath and get the same performance as on native. The above
> > numbers you got suggest that this is not the case. (your lat_ctx
> > numbers on native are probably around 1 usec, right?)
>
> Actually, native is around 5usec:
>
> # bin/x86_64-linux-gnu/lat_ctx -N 10 2
>
> "size=0k ovr=1.09
> 2 5.21
>
> So it does get pretty close to native, but the problem is that its
> difficult to see improvements on macrobenchmarks (even hackbench which
> remotely resembles a real scenario is not improving).

try running your shell on one CPU:

taskset -p 1 $$

that should give you the 'raw' single-CPU context switch results.

Ingo