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SubjectRe: [PATCH 2/5] Light Fragmentation Avoidance V20: 002_usemap
Mel Gorman wrote:

> That's iterating through, potentially, 1024 pages which I considered too
> expensive. In terms of code complexity, the page-flags patch adds 237
> which is not much of a saving in comparison to 275 that the usemap
> approach uses.

Surley you would just use a single bit in the first page of a MAX_ORDER
block. We guarentee that the mem_map is contigious out to MAX_ORDER
pages so you can simply calculate the offset. The page free path does
the same thing to find the buddy pages when coallescing.

> Again, I can revisit the page-flag approach if I thought that something
> like this would get merged and people would not choke on another page flag
> being consumed.

All of that said, I am not even sure we have a bit left in the page
flags on smaller architectures :/.

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