[RFC no patch yet] bootmem2: Another try

[Johannes Weiner <hannes@saeurebad.de>]

Hi,

my idea is now as follows:

Bootmem2 is block-oriented where a block represents a contiguous range
of physical memory.  Every block has a bitmap that keeps track of the
pages on it.

On top of this block interface, bootmem2 implements the node model
where a node can provide one or more memory blocks.

On configurations with multiple blocks per node, the arch code has to
register each block on its own.

free_bootmem and reserve_bootmem require that the requested range is
contiguous but they might go across node boundaries (two blocks on two
nodes can be contiguous).  For example:

node 0: block 0 = 0-2G, block 1 = 4-6G
node 1: block 2 = 2-4G, block 3 = 6-8G

free_bootmem(1.5G, 3G) is valid here, the range spans two nodes and two
blocks but is contiguous.

free_bootmem_node and reserve_bootmem_node are more strict, the ranges
have to be completely within one block of the specified node (two
blocks on one node are never contiguous).

alloc_bootmem_node tries to get memory between goal and limit from a
specific node and falls back to any free memory range on that node on
failure.

alloc_bootmem tries to get memory from between goal and limit and
falls back to any free memory range in the system on failure.

What do you say?

	Hannes