Re: -mm merge plans -- anti-fragmentation

[Andy Whitcroft <apw@shadowen.org>]

Andrew Morton wrote:
> On Tue, 10 Jul 2007 11:20:43 +0100
> mel@skynet.ie (Mel Gorman) wrote:
> 
>>> create-the-zone_movable-zone.patch
>>> allow-huge-page-allocations-to-use-gfp_high_movable.patch
>>> handle-kernelcore=-generic.patch
>>>
>>>  Mel's moveable-zone work.  In a similar situation.  We need to stop whatever
>>>  we're doing and get down and work out what we're going to do with all this
>>>  stuff.
>>>
>> Whatever about grouping pages by mobility, I would like to see these go
>> through. They have a real application for hugetlb pool resizing where the
>> administrator knows the range of hugepages that will be required but doesn't
>> want to waste memory when the required number of hugepages is small. I've
>> cc'd Kenneth Chen as I believe he has run into this problem recently where
>> I believe partitioning memory would have helped. He'll either confirm or deny.
> 
> Still no decision here, really.
> 
> Should we at least go for
> 
> add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated.patch
> create-the-zone_movable-zone.patch
> allow-huge-page-allocations-to-use-gfp_high_movable.patch
> handle-kernelcore=-generic.patch
> 
> in 2.6.23?

These patches are pretty simple and self-contained utilising the
existing zone infrastructure.  They provide a significant degree of
placement control when configured, which gives a lot of the benefits of
grouping-pages-by-mobility.  Merging these would seem like a low-risk
option.

Having a degree of placement control as delivered by ZONE_MOVABLE
greatly increases the effectiveness of lumpy reclaim at higher orders.
These patches plus lumpy would (IMO) provide a good base for further
development.  In particular I would envisage better usability for
hugepage users in terms of simpler configuration.

I would like to see ZONE_MOVABLE and lumpy considered for 2.6.23.

-apw