* Page alignment issue
@ 2006-12-27 15:49 Aubrey
2006-12-28 3:49 ` Aubrey
2006-12-31 6:02 ` Nick Piggin
0 siblings, 2 replies; 3+ messages in thread
From: Aubrey @ 2006-12-27 15:49 UTC (permalink / raw)
To: linux-kernel, linux-mm; +Cc: Nick Piggin
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? My problem seems to happen in
schedule()->context_switch() call, but so far I didn't figure out the
root cause.
Any clue or suggestion will be really appreciated!
Thanks,
-Aubrey
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Page alignment issue
2006-12-27 15:49 Page alignment issue Aubrey
@ 2006-12-28 3:49 ` Aubrey
2006-12-31 6:02 ` Nick Piggin
1 sibling, 0 replies; 3+ messages in thread
From: Aubrey @ 2006-12-28 3:49 UTC (permalink / raw)
To: linux-kernel, linux-mm; +Cc: Nick Piggin
On 12/27/06, Aubrey <aubreylee@gmail.com> 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? My problem seems to happen in
> schedule()->context_switch() call, but so far I didn't figure out the
> root cause.
It seems nothing depend on this feature. the problem you encounted is
the kernel task stack should be 2-page aligned.
-Aubrey
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Page alignment issue
2006-12-27 15:49 Page alignment issue Aubrey
2006-12-28 3:49 ` Aubrey
@ 2006-12-31 6:02 ` Nick Piggin
1 sibling, 0 replies; 3+ messages in thread
From: Nick Piggin @ 2006-12-31 6:02 UTC (permalink / raw)
To: Aubrey; +Cc: linux-kernel, linux-mm
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.
Send instant messages to your online friends http://au.messenger.yahoo.com
^ permalink raw reply [flat|nested] 3+ messages in thread
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