Re: [patch 4/5] slub: Use __GFP_MOVABLE for slabs of HPAGE_SIZE

[Christoph Lameter <clameter@sgi.com>]

On Thu, 14 Feb 2008, Pekka Enberg wrote:

> > This will make a system that was booted with
> > 
> > 	slub_min_order = 9
> > 
> > not have any reclaimable slab allocations anymore. All slab allocations
> > will be of type MOVABLE (although they are not movable like huge pages
> > are also not movable). This means that we only have MOVABLE and 
> > UNMOVABLE sections of memory which reduces the types of sections 
> > and therefore the danger of fragmenting memory.
> 
> Why does slub_min_order=9 matter? I suppose this is fixing some other
> real bug?

Because some people run slub with huge page allocations. It makes a lot of 
sense on systems that have more than 4 - 8G of RAM per cpu. The 2M pages 
for 100 slab caches (usually we have only 70) take 200M which is just a 
small fraction of the memory for one processor.

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