Re : sparsemem usage

From: moreau francis
Date: Wed Aug 02 2006 - 11:31:10 EST

Hi Alan !

Alan Cox wrote:
> The kernel allocates memory out using groups of blocks in a buddy
> system. 128K is smaller than one of the blocks so the kernel cannot
> handle this.

As I wrote to Andy Whitcroft, I would think that the kernel forbid allocation
of blocks whose size is greater than the current memorysize. But I know
nothing about the buddy allocator so I trust you ;)

> You need 2MB (if I remember right) granularity for your

MAX_ORDER is by default 11. Without changing this, I would say that I
need 4MB granularity.

> sections but nothing stops you marking most of the 2Mb section except
> the 128K that exists as "in use"

ok. But it will make pfn_valid() return "valid" for page beyond the first 128 KB.
Won't that result in bad impacts later ?



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