Re: the new VMt

Ingo Molnar
2000-09-25T16:02:18Z

On Mon, 25 Sep 2000, Andrea Arcangeli wrote:

> Ingo's point is that the underlined line won't ever happen in the
> first place

please dont misinterpret my point ...

Frankly, how often do we allocate multi-order pages? I've just made quick
statistics wrt. how allocation orders are distributed on a more or less
typical system:

(ALLOC ORDER)
0: 167081
1: 850
2: 16
3: 25
4: 0
5: 1
6: 0
7: 2
8: 13
9: 5

ie. 99.45% of all allocations are single-page! 0.50% is the 8kb
task-structure. The rest is 0.05%.

i'm not talking about 4MB contiguous physical allocations having to
succeed on a 8MB box. I'm talking about 99% of the simple allocation
points not having to worry about a NULL pointer. (not checking for NULL is
one of the most common allocation-related bug that beats low-RAM systems.)

Ingo