freebsd-skq/sys/sparc64
alc d74e85dbb9 Introduce pmap_unwire(). It will replace pmap_change_wiring(). There are
several reasons for this change:

pmap_change_wiring() has never (in my memory) been used to set the wired
attribute on a virtual page.  We have always used pmap_enter() to do that.
Moreover, it is not really safe to use pmap_change_wiring() to set the wired
attribute on a virtual page.  The description of pmap_change_wiring() says
that it assumes the existence of a mapping in the pmap.  However, non-wired
mappings may be reclaimed by the pmap at any time.  (See pmap_collect().)
Many implementations of pmap_change_wiring() will crash if the mapping does
not exist.

pmap_unwire() accepts a range of virtual addresses, whereas
pmap_change_wiring() acts upon a single virtual page.  Since we are
typically unwiring a range of virtual addresses, pmap_unwire() will be more
efficient.  Moreover, pmap_unwire() allows us to unwire superpage mappings.
Previously, we were forced to demote the superpage mapping, because
pmap_change_wiring() only allowed us to express the unwiring of a single
base page mapping at a time.  This added to the overhead of unwiring for
large ranges of addresses, including the implicit unwiring that occurs at
process termination.

Implementations for arm and powerpc will follow.

Discussed with:	jeff, marcel
Reviewed by:	kib
Sponsored by:	EMC / Isilon Storage Division
2014-07-06 17:42:38 +00:00
..
central
conf Restore comments accidentally removed. 2014-06-06 04:08:55 +00:00
ebus
fhc
include
isa
pci Pull in r267961 and r267973 again. Fix for issues reported will follow. 2014-06-28 03:56:17 +00:00
sbus
sparc64 Introduce pmap_unwire(). It will replace pmap_change_wiring(). There are 2014-07-06 17:42:38 +00:00