The biggie: Get rid of the UPAGES from the top of the per-process address

space. (!)

Have each process use the kernel stack and pcb in the kvm space.  Since
the stacks are at a different address, we cannot copy the stack at fork()
and allow the child to return up through the function call tree to return
to user mode - create a new execution context and have the new process
begin executing from cpu_switch() and go to user mode directly.
In theory this should speed up fork a bit.

Context switch the tss_esp0 pointer in the common tss.  This is a lot
simpler since than swithching the gdt[GPROC0_SEL].sd.sd_base pointer
to each process's tss since the esp0 pointer is a 32 bit pointer, and the
sd_base setting is split into three different bit sections at non-aligned
boundaries and requires a lot of twiddling to reset.

The 8K of memory at the top of the process space is now empty, and unmapped
(and unmappable, it's higher than VM_MAXUSER_ADDRESS).

Simplity the pmap code to manage process contexts, we no longer have to
double map the UPAGES, this simplifies and should measuably speed up fork().

The following parts came from John Dyson:

Set PG_G on the UPAGES that are now in kernel context, and invalidate
them when swapping them out.

Move the upages object (upobj) from the vmspace to the proc structure.

Now that the UPAGES (pcb and kernel stack) are out of user space, make
rfork(..RFMEM..) do what was intended by sharing the vmspace
entirely via reference counting rather than simply inheriting the mappings.

1 files changed, 1 insertions, 2 deletions

diff --git a/sys/vm/vm_map.h b/sys/vm/vm_map.h
index d1905ad64613..8438ccf08d26 100644
--- a/sys/vm/vm_map.h
+++ b/sys/vm/vm_map.h
@@ -61,7 +61,7 @@
  * any improvements or extensions that they make and grant Carnegie the
  * rights to redistribute these changes.
  *
- * $Id: vm_map.h,v 1.24 1997/02/22 09:48:24 peter Exp $
+ * $Id: vm_map.h,v 1.25 1997/04/06 02:29:44 dyson Exp $
  */
 
 /*
@@ -152,7 +152,6 @@ struct vmspace {
 	struct pmap vm_pmap;	/* private physical map */
 	int vm_refcnt;		/* number of references */
 	caddr_t vm_shm;		/* SYS5 shared memory private data XXX */
-	vm_object_t vm_upages_obj;	/* UPAGES object */
 /* we copy from vm_startcopy to the end of the structure on fork */
 #define vm_startcopy vm_rssize
 	segsz_t vm_rssize;	/* current resident set size in pages */