copy on write memory

[Peri Hankey <mpah@thegreen.co.uk>]

Hello

UML has developed a SKAS mode of operation, in which (as far as I 
understand it) a process can be created much in the same way as any 
other Linux process, except that it runs (under an UML kernel) with a 
separate kernel address space.

It occurred to me that the equivalent in the Xen world would be to use 
one Linux xenU domain purely as a page-table manager for a collection of 
separate xenU domains that are expected or known have similar process 
populations. The process creation domain would have a large allocation 
of memory which it would use to populate page tables applying standard 
copy on write semantics, but the processes to which these page tables 
belong would effectively run in the separate execution domains to which 
they belong.

A similar arrangement of one page-table management domain with multiple 
separate execution domains could be used for other kernels such as 
netbsd, which have similar copy on write semantics.

Xen itself would only need to provide a mechanism for managing the trade 
between a page-manager domain and its execution domains, and would not 
need to replicate the functionality of any particular system.

As the page-table manager domain also knows which disk pages are clean, 
and which have been written to, it is also in a good position to manage 
copy on write semantics for filesystem storage.

Is this a feasible way of looking at it?

Regards
Peri Hankey



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