Re: [PATCH 2/5] Light Fragmentation Avoidance V20: 002_usemap

[Andi Kleen]

On Wednesday 16 November 2005 02:43, Mel Gorman wrote:

> 1. I was using a page flag, valuable commodity, thought I would get kicked
>    for it. Usemap uses 1 bit per 2^(MAX_ORDER-1) pages. Page flags uses
>    2^(MAX_ORDER-1) bits at worse case.

Why does it need multiple bits? A page can only be in one order at a
time, can't it?

> 2. Fragmentation avoidance tended to break down, very fast.

Why? The algorithm should the same, no?

> 3. When changing a block of pages from one type to another, there was no
>    fast way to make sure all pages currently allocation would end up on
>    the correct free list

If you can change the bitmap you can change as well mem_map

-Andi
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