Re: Avoiding external fragmentation with a placement policy Version 12

Christoph Lameter
2005-06-10T16:20:15Z

On Wed, 8 Jun 2005, Martin J. Bligh wrote:

> Right. I agree that large allocs should be reliable. Whether we care so
> much about if they're performant or not, I don't know ... is an interesting
> question. I think the answer is maybe not, within reason. The cost of
> fishing in the allocator might well be irrelevant compared to the cost
> of freeing the necessary memory area?

Large consecutive page allocation is important for I/O. Lots of drivers
are able to issue transfer requests spanning multiple pages which is only
possible if the pages are in sequence. If memory is fragmented then this
is no longer possible.