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Re: [XenPPC] [RFC] 64mb Chunk Allocator

On Thu, 2006-06-22 at 16:39 -0400, Dan E Poff wrote:
> For Xen on PPC, each domain needs a section of real memory, starting
> at 'real address' 0x0, allowing code to run with translate off. The
> PPC LPAR facility allows a unique chunk of memory to be 'mapped' at
> real address 0x0 for each partition (via RMOR). Minimum size of a
> chunk is 64mb, and requires alignment. Today's Xen code sets-up a
> single 64mb chunk for each domain. 

That's being generous. I would rather say "today's Xen code ignores
memory management altogether and clobbers chunks." :)

> Proposal: (my interpretation of Jimi's ideas...) 
>         Simple 64mb chunk allocator, allowing multiple chunks per
> domain, and freeing chunks when a domain is destroyed 

I don't see that we need multiple chunks per domain.

> Implementation: 
>         - Find installed memory using 'ofd' structure. Currently
> memory discovery stops at 1st hole (whether I/O or sparse). 
>         - Use bit-vector to indicate available chunks; atomic updating
> for SMP 
>         - Linux 'sparse memory support' will allow holes between 64mb
> chunks within domain 

You're planning to use fixed-size 64MB chunks? I don't have a problem
with that, but it's worth stating explicitly.

Hollis Blanchard
IBM Linux Technology Center

Xen-ppc-devel mailing list

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