Re: [9fans] Virtual memory in BSD and Plan9

[Borja Marcos <borjamar@sarenet.es>]

On Monday 29 October 2001 13:38, you wrote:
> I'm a radical here, but I think if a machine is paging, you've lost.
> To me, VM is a pretty technique for memory management in the kernel,
> something distinct from paging, which is a way to get the system
> through temprorary overshoots in memory demand.

	That's right. Virtual memory avoids, for example, the memory fragmentation 
problem. Memory is divided into fixed-size pages, and the address space of a 
process doesn't need to be contiguous. Processes see a "logical" address 
space which is translated to physical addresses by the MMU.

	So, virtual memory is in my opinion a very good thing.

	Regarding paging, it depends on *how* much does it page. I don't mind if my 
machine has to page sometimes. There are rules of thumb that specify a degree 
of "acceptable badness". ;-)




	Borja.