Re: [Lhms-devel] Re: [RFC] free_area[] bitmap elimination [0/3]

Hiroyuki KAMEZAWA
2004-08-21T05:21:42Z

Hi,
Hirokazu Takahashi wrote:

> Hi,
>
>
>>William Lee Irwin III wrote:
>>
>>
>>>On Sat, Aug 21, 2004 at 11:31:21AM +0900, Hiroyuki KAMEZAWA wrote:
>>>
>>>
>>>>This patch removes bitmap from buddy allocator used in
>>>>alloc_pages()/free_pages() in the kernel 2.6.8.1.
<snip>
>>In my understanding, the patch assumes that size of mem_map[] in each
>>zone must be multiple of 2^MAX_ORDER, right?
>>But it doesn't seem it's a big problem, as we can just allocate extra
>>mem_map[] to round up if it isn't.
>
>
> I think this may help the buddy allocator to work withtout adding
> page_ivs_valid(buddy1).
>
>
As you say, I expects the size of zone is multiple of MAX_ORDER.
But IA64 kernel's MAX_ORDER is 4 Giga bytes :(
A Tiger4, an IA64 machine, I use has physical memory map like this:

0-2G :
4-8G :
10-12G:

contiguous mem_map is smaller than MAX_ORDER.

So I think page_is_valid(buddy1) is needed only for a few pages,
which is top of big buddy, in this case.

Hmm.... :(

Thank you,
KAME

--
--the clue is these footmarks leading to the door.--
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>