Re: Page alignment issue

From: Nick Piggin
Date: Sun Dec 31 2006 - 01:03:59 EST

Aubrey wrote:
As for the buddy system, much of docs mention the physical address of
the first page frame of a block should be a multiple of the group
size. For example, the initial address of a 16-page-frame block should
be 16-page aligned. I happened to encounted an issue that the physical
addresss pf the block is not 4-page aligned(0x36c9000) while the order
of the block is 2. I want to know what out of buddy algorithm depend
on this feature?

I think that's correct. The buddy allocator uses bitwise operations to
find buddy pages and promote free pairs (eg. see __page_find_buddy()
and __find_combined_index()).

SUSE Labs, Novell Inc.
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