Enable the new physical memory allocator.

This allocator uses a binary buddy system with a twist.  First and
foremost, this allocator is required to support the implementation of
superpages.  As a side effect, it enables a more robust implementation
of contigmalloc(9).  Moreover, this reimplementation of
contigmalloc(9) eliminates the acquisition of Giant by
contigmalloc(..., M_NOWAIT, ...).

The twist is that this allocator tries to reduce the number of TLB
misses incurred by accesses through a direct map to small, UMA-managed
objects and page table pages.  Roughly speaking, the physical pages
that are allocated for such purposes are clustered together in the
physical address space.  The performance benefits vary.  In the most
extreme case, a uniprocessor kernel running on an Opteron, I measured
an 18% reduction in system time during a buildworld.

This allocator does not implement page coloring.  The reason is that
superpages have much the same effect.  The contiguous physical memory
allocation necessary for a superpage is inherently colored.

Finally, the one caveat is that this allocator does not effectively
support prezeroed pages.  I hope this is temporary.  On i386, this is
a slight pessimization.  However, on amd64, the beneficial effects of
the direct-map optimization outweigh the ill effects.  I speculate
that this is true in general of machines with a direct map.

Approved by:	re

1 files changed, 18 insertions, 0 deletions

diff --git a/sys/powerpc/include/vmparam.h b/sys/powerpc/include/vmparam.h
index 01a29b2..60e240c 100644
--- a/sys/powerpc/include/vmparam.h
+++ b/sys/powerpc/include/vmparam.h
@@ -109,9 +109,27 @@ struct pmap_physseg {
  */
 #define	VM_PHYSSEG_DENSE
 
+/*
+ * Create two free page pools: VM_FREEPOOL_DEFAULT is the default pool
+ * from which physical pages are allocated and VM_FREEPOOL_DIRECT is
+ * the pool from which physical pages for small UMA objects are
+ * allocated.
+ */
+#define	VM_NFREEPOOL		2
+#define	VM_FREEPOOL_DEFAULT	0
+#define	VM_FREEPOOL_DIRECT	1
+
+/*
+ * Create one free page list.
+ */
 #define	VM_NFREELIST		1
 #define	VM_FREELIST_DEFAULT	0
 
+/*
+ * The largest allocation size is 4MB.
+ */
+#define	VM_NFREEORDER		11
+
 #ifndef VM_INITIAL_PAGEIN
 #define	VM_INITIAL_PAGEIN	16
 #endif