On Oct 17,  1:16pm, Thomas Down (RiscBSD list) wrote:
> Subject: Re: SA110 - Current status

[ snip ]

> This may sound a rather strange idea, and certainly isn't a short
> term fix, but how easy would it be to replace the current context
> switching system with a mechanism whereby all application binaries
> are relocatable, and are loaded at their own address. At this
> point, a context switch would simply envolve marking all the pages
> containing the current application as inaccessable, and those
> containing the next as accessable, then jumping into the next
> application. This would present some new difficulties---memory
> allocation will probably have to be redesigned so that an
> application can own several heap blocks in totally differant
> areas of memory (otherwise it will be necessary to decide
> the total maximum amount of memory an application will _ever_
> be allowed to use at load time.

In theory it would be possible. I think this comes under the heading of
'writing a new operating system' though. Unfortunately you would still have
problems because the memory-protection also relies on cache flushing. This does
truely horrible things to our dirty-bit emulation and means that SA RiscBSD is
probably prone to paging out its working-set.

Cheers

Rob

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