Re: [PATCH 0/6] mm/hugetlb: gigantic hugetlb page pools shrinksupporting

[Andi Kleen]

On Fri, Apr 12, 2013 at 07:29:07AM +0800, Wanpeng Li wrote:
> Ping Andi,
> On Thu, Apr 04, 2013 at 05:09:08PM +0800, Wanpeng Li wrote:
> >order >= MAX_ORDER pages are only allocated at boot stage using the 
> >bootmem allocator with the "hugepages=xxx" option. These pages are never 
> >free after boot by default since it would be a one-way street(>= MAX_ORDER
> >pages cannot be allocated later), but if administrator confirm not to 
> >use these gigantic pages any more, these pinned pages will waste memory
> >since other users can't grab free pages from gigantic hugetlb pool even
> >if OOM, it's not flexible.  The patchset add hugetlb gigantic page pools
> >shrink supporting. Administrator can enable knob exported in sysctl to
> >permit to shrink gigantic hugetlb pool.


I originally didn't allow this because it's only one way and it seemed
dubious.  I've been recently working on a new patchkit to allocate
GB pages from CMA. With that freeing actually makes sense, as 
the pages can be reallocated.

-Andi
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