Re: Avoiding external fragmentation with a placement policy Version 12

Mike Kravetz
2005-06-01T23:47:33Z

On Thu, Jun 02, 2005 at 09:09:23AM +1000, Nick Piggin wrote:
>
> It adds a lot of complexity to the page allocator and while
> it might be very good, the only improvement we've been shown
> yet is allocating lots of MAX_ORDER allocations I think? (ie.
> not very useful)
>

Allocating lots of MAX_ORDER blocks can be very useful for things
like hot-pluggable memory. I know that this may not be of interest
to most. However, I've been combining Mel's defragmenting patch
with the memory hotplug patch set. As a result, I've been able to
go from 5GB down to 544MB of memory on my ppc64 system via offline
operations. Note that ppc64 only employs a single (DMA) zone. So,
page 'grouping' based on use is coming mainly from Mel's patch.

--
Mike