Re: [PATCH 1/4] compcache: xvmalloc memory allocator

[Christoph Lameter]

On Tue, 25 Aug 2009, Nitin Gupta wrote:

> PFNs are 32-bit on all archs while for 'struct page *', we require 32-bit or
> 64-bit depending on arch. ramzswap allocates a table entry <pagenum, offset>
> corresponding to every swap slot. So, the size of table will unnecessarily
> increase on 64-bit archs. Same is the argument for xvmalloc free list sizes.

Wrong. PFNs must be longer than 32 bit otherwise a system cannot
address more than 2^12 + 2^32 = 2^44 =>  16TB.

The type used for PFNs is unsigned long which are 64 bit on 64 bit platforms.

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