Re: Avoiding external fragmentation with a placement policy Version 12

Martin J. Bligh
2005-06-03T14:00:59Z

> Does it need more documentation? If so, I'll write up a detailed blurb on
> how it works and drop it into Documentation/
>
>> Although I can't argue that a buddy allocator is no good without
>> being able to satisfy higher order allocations.
>
> Unfortunately, it is a fundemental flaw of the buddy allocator that it
> fragments badly. The thing is, other allocators that do not fragment are
> also slower.

Do we care? 99.9% of allocations are fronted by the hot/cold page cache
now anyway ... and yes, I realise that things popping in/out of that
obviously aren't going into the "defrag" pool, but still, it should help.
I suppose all we're slowing down is higher order allocs anyway, which
is the uncommon case, but ... worth thinking about.

M.