[cap-talk] Cap type safe OS questions

[Sam Mason]

On Mon, Aug 03, 2009 at 01:38:03AM +0800, Ben Kloosterman wrote:
> I think this is mainly due to the high Context switch costs of the common
> separate user address space , multiple privilege levels OS. The Singularity
> paper " Singularity - Rethinking the Software Stack " shows good performance
> with an Asych  IPC with an unoptomized kernel compared to L4.  

I was under the impression so far that you had two address spaces, one
for the kernel and one for everything else.  The way you've been talking
about the kernel fiddling with message queues would suggest that you
have five address space switches per invocation:

  user -> kernel -> user -> kernel -> user

and you hence you seem to be more similar to L4.  Singularity is single
address space and there are no context switches at all.


This is getting a long way off normal cap-talk territory though!

-- 
  Sam  http://samason.me.uk/