Re: Tonight's tradeoff

On 2024-03-08 2:41 p.m., George Neuner wrote:

On Thu, 7 Mar 2024 16:02:45 -0500, Robert Finch <robfi680@gmail.com>
wrote:
 

A page marked RWE=000 is an unusable page. Perhaps to signal bad memory.
Or perhaps as a hidden data page full of comments or remarks. If its not
readable-writeable or executable what is it? Nothing should be able to
access it, except maybe the machine/debug operating mode.

 The ability to change (at least data) pages between "untouchable" and
RW is required for MMU assisted incremental GC.  If the GC also
handles code, then it must be able to mark pages executable as well.
 If an "untouchable" page can't be manipulated by user software, then
you've disallowed an entire class of GC systems.

Garbage collection seems to be common.
I plan on having garbage collection as part of the OS. There is a shared hardware-card table involved. So, I guess that would disallow user garbage collectors using untouchable pages. The MMU could be faked out using a VM, so I have read.