[cap-talk] Cap type safe OS questions

[Sam Mason]

On Sun, Aug 02, 2009 at 03:48:39PM +0800, Ben Kloosterman wrote:
> At present the kernel only access "user" address spaces to add
> received messages to the queue

Most of the micro-kernel research (i.e. just not ocap related) says
that unbuffered, synchronous IPC is the easiest way to get reasonable
performance.

The L4 work has a few good documents on this and a lot of the EROS work
is very complementary to this; the following are a fun set:

  http://l4ka.org/publications/1996/ukernels-must-be-small.pdf
  http://www.eros-os.org/papers/iwooos96-ipc.ps
  http://srl.cs.jhu.edu/~shap/proposal/proposal.ps

As I understand it, the effects of cache dominate when you're doing lots
of little calls and returns and hence it makes sense to try and keep
the data they're working with in cache and hence temporal clustering is
important.  As soon as you're dealing with queues of messages you've got
two new problems, the temporal clustering is broken and even if not you
got even more cache pressure and data-dependent operations.


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