On Thu, 14 Sep 2006, Michael van Elst wrote:

> mhitch@gemini.msu.montana.edu ("Michael L. Hitch") writes:
>
> >  And it was indeed using a cached page for the segment tables.  The uvm
> >changes resulted in the page allocated for the segment tables to be
> >entered in a manner that the current method of makeing the page non-cached
> >no longer works.  I have fixed the amiga pmap to directly change the PTE
> >bits and my amiga now is quite happy, without excessive faulting.
>
> Would setting NKPTADD=8 make the fault less likely?

  I suspect that anything which changes the data cache usage pattern would
affect it.  If the cache line containing the level 2 segment pointer takes
a long time to get written back to memory, page faults will continue until
the cache line gets written.  If that cache line is indexed by many other
data accesses that occur frequently, it would get written much sooner.

  A real good example is when I added code to keep a history of faults to
the trap routine.  The kernel I ran before the change was taking several
minutes to just get to the single-user shell prompt.  After adding the
debug code, the page faulting was almost unnoticable - until I looked at
the fault history that I had added.

Michael