Add a new physical memory allocator. However, do not yet connect it

to the build.

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, 52 insertions, 0 deletions

diff --git a/sys/vm/vm_phys.h b/sys/vm/vm_phys.h
new file mode 100644
index 0000000..4d34ccf
--- /dev/null
+++ b/sys/vm/vm_phys.h
@@ -0,0 +1,52 @@
+/*-
+ * Copyright (c) 2002-2006 Rice University
+ * All rights reserved.
+ *
+ * This software was developed for the FreeBSD Project by Alan L. Cox,
+ * Olivier Crameri, Peter Druschel, Sitaram Iyer, and Juan Navarro.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
+ * HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
+ * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+/*
+ *	Physical memory system definitions
+ */
+
+#ifndef	_VM_PHYS_H_
+#define	_VM_PHYS_H_
+
+void vm_phys_add_page(vm_paddr_t pa);
+vm_page_t vm_phys_alloc_contig(unsigned long npages,
+    vm_paddr_t low, vm_paddr_t high,
+    unsigned long alignment, unsigned long boundary);
+vm_page_t vm_phys_alloc_pages(int pool, int order);
+vm_page_t vm_phys_alloc_pages_locked(int pool, int order);
+vm_paddr_t vm_phys_bootstrap_alloc(vm_size_t size, unsigned long alignment);
+void vm_phys_free_pages(vm_page_t m, int order);
+void vm_phys_free_pages_locked(vm_page_t m, int order);
+void vm_phys_init(void);
+boolean_t vm_phys_zero_pages_idle(void);
+
+#endif	/* !_VM_PHYS_H_ */