Re: [uml-user] Performance Optimizations

[Matthew B. <ma...@by...>]

On Friday 08 November 2002 23:09, Ian C. Blenke wrote:
> On Friday 08 November 2002 16:53, David Coulson wrote:
> > Steven Tower wrote:
> > > Are there any tips/tricks for performance optimizations for uml
> > > sessions?
> >
> > 1) Mount /tmp as a tmpfs filesystem
> > 2) For lots of UMLs, use COW with a single backing store
>
> Using COWs with a single backing store only seems to impede performance,
> not improve it. If you're looking for performance, strongly reconsider
> unique images for each UML instance.

Does anyone know why this is the case?  Like I said earlier, I assumed that 
having the kernel being able to cache a bunch of commonly-used disc blocks in 
memory, especially if they were shared between many UMLs, would improve 
performance.  I can understand that COW discs may be slower intrinsically 
because the kernel would have to potentially check two disc blocks rather 
than one per read.

-- 
Matthew Bloch         Bytemark Computer Consulting Limited
                                http://www.bytemark.co.uk/
                                  tel. +44 (0) 8707 455026