Re: [crash] Re: Latest brk patchset

[H. Peter Anvin]

Jeremy Fitzhardinge wrote:
> Yinghai Lu wrote:
> > could be max_pfn_mapped change in head_32.S that reduce mapping range 
> > to _end only.
> >   
>
> Yes, I would say you're right.  Trimming the mapping to _end only leaves 
> the space under the kernel avaliable for allocating pagetable from e820 
> space.  In this case we've got DEBUG_PAGEALLOC enabled, which inhibits 
> the use of PSE, and BIOS corruption checking on, which eats a chunk of 
> low memory.  In combination, there's only 0x8f000 bytes free below the 
> kernel, and it needs 0xe1000 to allocate for pagetables.
>
> Reverting 2bd2753ff46346543ab92e80df9d96366e21baa5 fixes the problem for 
> me, though it does result in a kernel with a 73MB BSS...

Waitaminute... there is no way we could end up with 73 MB page tables 
unless something is seriously screwy.  Even with PAE and !PSE, we only 
get 2 MB worth of page tables for each 1 GB mapped -- even with a 4:4 
scheme this is only 8 MB.

	-hpa

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