linux-kernel - Re: Page alignment issue

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Message-ID: <45975274.6020909@yahoo.com.au>
Date:	Sun, 31 Dec 2006 17:02:28 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Aubrey <aubreylee@...il.com>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: Page alignment issue

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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