Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Refactor vm_page_alloc()'s interactions with vm_reserv_alloc_page() and
vm_page_insert() so that (1) vm_radix_lookup_le() is never called while the
free page queues lock is held and (2) vm_radix_lookup_le() is called at most
once. This change reduces the average time that the free page queues lock
is held by vm_page_alloc() as well as vm_page_alloc()'s average overall
running time.

Sponsored by: EMC / Isilon Storage Division

Introduce vm_reserv_alloc_contig() and teach vm_page_alloc_contig() how to
use superpage reservations. So, for the first time, kernel virtual memory
that is allocated by contigmalloc(), kmem_alloc_attr(), and
kmem_alloc_contig() can be promoted to superpages. In fact, even a series
of small contigmalloc() allocations may collectively result in a promoted
superpage.

Eliminate some duplication of code in vm_reserv_alloc_page().

Change the type of vm_reserv_reclaim_contig()'s first parameter in order
that it be consistent with other vm_*_contig() functions.

Tested by: marius (sparc64)

Eliminate vm_phys_bootstrap_alloc(). It was a failed attempt at
eliminating duplicated code in the various pmap implementations.

Micro-optimize vm_phys_free_pages().

Introduce vm_phys_free_contig(). It is fast routine for freeing an
arbitrary number of physically contiguous pages. In particular, it
doesn't require the number of pages to be a power of two.

Use "u_long" instead of "unsigned long".

Bruce Evans (bde@) has convinced me that the "boundary" parameters
to kmem_alloc_contig(), vm_phys_alloc_contig(), and
vm_reserv_reclaim_contig() should be of type "vm_paddr_t" and not
"u_long". Make this change.

Introduce vm_reserv_reclaim_contig(). This function is used by
contigmalloc(9) as a last resort to steal pages from an inactive,
partially-used superpage reservation.

Rename vm_reserv_reclaim() to vm_reserv_reclaim_inactive() and
refactor it so that a separate subroutine is responsible for breaking
the selected reservation. This subroutine is also used by
vm_reserv_reclaim_contig().

Add the superpage reservation system. This is "part 2 of 2" of the
machine-independent support for superpages. (The earlier part was
the rewrite of the physical memory allocator.) The remainder of the
code required for superpages support is machine-dependent and will
be added to the various pmap implementations at a later date.

Initially, I am only supporting one large page size per architecture.
Moreover, I am only enabling the reservation system on amd64. (In
an emergency, it can be disabled by setting VM_NRESERVLEVELS to 0
in amd64/include/vmparam.h or your kernel configuration file.)