🚀 go-pugleaf

In article <1993Jan21.195003.6023@ictv.com> barry@ictv.com (Barry Lustig) writes:
     There has been speculation recently about whether a NeXT can swap to
   a raw partition or not.  I decided to do a little research on this
   point and found out that you cannot.  The reason for this should be
   clear from the following:

       Current directory is /
       Reading symbol data from sdmach...
       (no debugging symbols found)...done.
       (gdb) disassemble swapon
       Dump of assembler code for function swapon:
       0x4068288 <swapon>:	rts
       End of assembler dump.
       (gdb) 

   NeXT removed the code for the swapon system call from the kernel.
   They would have made life a lot easier for people if they also removed
   the call from the system library.

Not quite so fast. All you found out that the BSD system call to
enable swaping is a dummy call. From that one might conclude that the
NeXT can not swap at all just as quickly as that it can not swap to a
raw partition.  Fortunately that is not so as virtual memory is one of
the system services which is provided by Mach through the mach_swapon
system call and not BSD on a NeXT. And mach_swapon is _not_ a dummy
call. Careful analysis of this call and its subroutines might reveal
that indeed it is impossible to swap to a raw partition (as I believe
it is). This analysis is left as an exercise to the reader.

        Carl Edman

In article <CEDMAN.93Jan21153237@capitalist.princeton.edu> cedman@princeton.edu (Carl Edman) writes:
	Not quite so fast. All you found out that the BSD system call to
	enable swaping is a dummy call. From that one might conclude that the
	NeXT can not swap at all just as quickly as that it can not swap to a
	raw partition.  Fortunately that is not so as virtual memory is one of
	the system services which is provided by Mach through the mach_swapon
	system call and not BSD on a NeXT. And mach_swapon is _not_ a dummy
	call. Careful analysis of this call and its subroutines might reveal
	that indeed it is impossible to swap to a raw partition (as I believe
	it is). This analysis is left as an exercise to the reader.
	
	        Carl Edman


  As I mentioned to Carl in a mail message, I did look at mach_swapon
as well.  As far as I can tell, mach_swapon uses the vnode pager code.
This provides for paging to a file, not to a raw device.  

  One can also look at the virtual memory sub-system of 386bsd or
Berkeley net-2.  Both of them use the mach virtual memory system.

barry
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