Introduce a new mechanism for relocating virtual pages to a new physical
address and use this mechanism when:
- 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.
- 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
- 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