Introduce a new mechanism for relocating virtual pages to a new physical

address and use this mechanism when:

1. kmem_alloc_{attr,contig}() can't find suitable free pages in the physical
   memory allocator's free page lists.  This replaces the long-standing
   approach of scanning the inactive and inactive queues, converting clean
   pages into PG_CACHED pages and laundering dirty pages.  In contrast, the
   new mechanism does not use PG_CACHED pages nor does it trigger a large
   number of I/O operations.

2. on 32-bit MIPS processors, uma_small_alloc() and the pmap can't find
   free pages in the physical memory allocator's free page lists that are
   covered by the direct map.  Tested by: adrian

3. ttm_bo_global_init() and ttm_vm_page_alloc_dma32() can't find suitable
   free pages in the physical memory allocator's free page lists.

In the coming months, I expect that this new mechanism will be applied in
other places.  For example, balloon drivers should use relocation to
minimize fragmentation of the guest physical address space.

Make vm_phys_alloc_contig() a little smarter (and more efficient in some
cases).  Specifically, use vm_phys_segs[] earlier to avoid scanning free
page lists that can't possibly contain suitable pages.

Reviewed by:	kib, markj
Glanced at:	jhb
Discussed with:	jeff
Sponsored by:	EMC / Isilon Storage Division
Differential Revision:	https://reviews.freebsd.org/D4444

1 files changed, 4 insertions, 0 deletions

diff --git a/sys/vm/vm_page.h b/sys/vm/vm_page.h
index a1f6fc405681..972603a04b98 100644
--- a/sys/vm/vm_page.h
+++ b/sys/vm/vm_page.h
@@ -474,6 +474,8 @@ vm_page_t vm_page_prev(vm_page_t m);
 boolean_t vm_page_ps_is_valid(vm_page_t m);
 void vm_page_putfake(vm_page_t m);
 void vm_page_readahead_finish(vm_page_t m);
+bool vm_page_reclaim_contig(int req, u_long npages, vm_paddr_t low,
+    vm_paddr_t high, u_long alignment, vm_paddr_t boundary);
 void vm_page_reference(vm_page_t m);
 void vm_page_remove (vm_page_t);
 int vm_page_rename (vm_page_t, vm_object_t, vm_pindex_t);
@@ -482,6 +484,8 @@ vm_page_t vm_page_replace(vm_page_t mnew, vm_object_t object,
 void vm_page_requeue(vm_page_t m);
 void vm_page_requeue_locked(vm_page_t m);
 int vm_page_sbusied(vm_page_t m);
+vm_page_t vm_page_scan_contig(u_long npages, vm_page_t m_start,
+    vm_page_t m_end, u_long alignment, vm_paddr_t boundary, int options);
 void vm_page_set_valid_range(vm_page_t m, int base, int size);
 int vm_page_sleep_if_busy(vm_page_t m, const char *msg);
 vm_offset_t vm_page_startup(vm_offset_t vaddr);