1. Make the caller responsible for performing pmap_install(). This reduces
the number of times that pmap_install() is performed by
pmap_enter_object() from twice per page to twice overall.
2. Don't block if pmap_find_pte() is unable to allocate a PTE. If it did
block, then it might wind up mapping a cache page. Specifically, if
pmap_enter_quick_locked() slept when called from pmap_enter_object(), the
page daemon could change an active or inactive page into a cache page just
before it was to be mapped.
3. Bail out of pmap_enter_quick_locked() if pv entries aren't plentiful.
In other words, don't force the allocation of a pv entry if they aren't
readily available.
Reviewed by: marcel@
9b123ca12a