yeah - sorry about that impatient flame. And it could still be anything
from the page allocator to bootmem - or some completely unrelated piece
of code corrupting some key data structure.
sparsemem is supposed to work roughly like this on x86 (32-bit):
- the x86 memory map comes from the bios via e820.
- those individual chunks of e820-enumerated memory get
registered with mm/sparse.c's data structures via memory_present()
callbacks. [btw., this should be renamed to register_memory_present()
or register_sparse_range() - something less opaque.]
- there's really just 3 RAM areas that matter on this box, and the last
one is unusable for !PAE, which leaves 2.
- there's a 256 MB PCI aperture hole at 0xf0000000.
- out of the 64 sparse memory chunk the first 60 get filled in (all have
at least partially some RAM content) - the last 4 [the PCI aperture
hole] remains !present.
- we pass in an array of 3 zones to free_area_init_nodes().
- we free the lowmem pages into the buddy allocator via the usual
generic setup
- we have a special loop for highmem pages in arch/x86/mm/init_32.c,
set_highmem_pages_init(). This just goes through the PFNs one by one
and does an explicit __free_page() on all RAM pages that are in the
mem_map[] and which are non-reserved.
and that's it roughly.
my current guess would have been some bootmem regression/interaction
that messes up the buddy bitmaps - but i just reverted to the v2.6.24
version of bootmem.c and that crashes too ...
Ingo
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