Hi,

William Lee Irwin III wrote:

quoted

On Sat, Aug 21, 2004 at 11:31:21AM +0900, Hiroyuki KAMEZAWA wrote:

quoted

This patch removes bitmap from buddy allocator used in
alloc_pages()/free_pages() in the kernel 2.6.8.1.

<snip>

quoted

Complexity maybe. But one serious issue this addresses beyond the needs
of hotplug memory is that the buddy bitmaps are a heavily random-access
data structures not used elsewhere. Consolidating them into the page
structures should improve cache locality and motivate this patch beyond
just the needs of hotplug memory. Furthermore, the patch also reduces
the kernel's overall memory footprint by a small amount.

However, I'm concerned about the effectiveness of this specific
algorithm for coalescing. A more detailed description may help explain
why the effectiveness of coalescing is preserved.

Thanks for your comment, William-san.
I'd like to add detailed description on my patch.
I'm now afraid of the case of memory-hole, I should add page_ivs_valid(buddy1) before
accessing buddy1.

What do you think about my idea I just posted.

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).


Thank you,
Hirokazu Takahashi.
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