cvs commit: src/sys/ia64/ia64 exception.S interrupt.c machdep.c mp_machdep.c pmap.c trap.c vm_machdep.c src/sys/ia64/include proc.h smp.h

[Marcel Moolenaar]

On Aug 7, 2005, at 1:41 AM, Doug Rabson wrote:

> Excellent! When trying to think about per-cpu VHPT in the past, I  
> could
> never quite see how to handle the collision chains sanely. The  
> solution
> described below seems ideal.

I'm quite happy with it as well. The hash bucket head structure  
allows for
the collection of per-bucket statistics. I already have a length field
that holds the length of the chain (or number of PTEs in the bucket).  
What
I'd like to do is get a better sense of how critical it is if there's a
VHPT miss. Maybe we can implement the code that handles it in C, use  
locks
and open the doors to having various different hash bucket  
implementations
to play with. I still have my concerns about the assembly in exception.S
and the lack of locking therein. This in the context of having spurious
core dumps.

In parallel, I'm measuring the effect on performance of bumping up  
the page
size to 16K and 32K. I suspect the cost of a VHPT miss is mostly due  
to us
needing to find the PTE in the hash bucket by walking a linked list.  
Keeping
the average length of the list small may improve our overall  
performance.

Lots to learn...

-- 
  Marcel Moolenaar         USPA: A-39004          marcel at xcllnt.net