Accounting for missing ( bootmem? ) memory

[Phillip Susi <psusi@ubuntu.com>]

I've been trying to track down why free always seems to report a little 
less total ram than it should, compared to the total usable areas in the 
e820 memory map.  I have been reading mm/bootmem.c and it seems that the 
low memory zone is managed by this allocator prior to mm_init(), and 
then free_all_bootmem() is called, which releases all free bootmem pages 
to mm to handle, and adds that space to totalram_pages.  That means that 
any bootmem that is still allocated is lost from the totalram_pages count.

I'm trying to figure out what is consuming this bootmem.  Based on 
comments in bootmem.c, the memory is initially marked as allocated, and 
setup_arch() has to explicitly free any that isn't reserved, presumably 
for things like the kernel itself, and the initrd, and any reserved 
areas in the e820 map, but I can not find where this is done.

So my questions are:

1)  Where is the bootmem initially freed ( so I can see what sections 
are *not* initially freed )

2)  Why is all of the bootmem not reserved in the e820 map not 
eventually freed and turned over to mm to manage?

3)  How can I see what is allocating and never freeing bootmem?

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