Re: [RFC PATCH] page_cgroup: Reduce allocation overhead forpage_cgroup array for CONFIG_SPARSEMEM

[KAMEZAWA Hiroyuki]

On Wed, 23 Feb 2011 10:19:22 -0800
Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote:

> On Wed, 2011-02-23 at 16:10 +0100, Michal Hocko wrote:
> > We can reduce this internal fragmentation by splitting the single
> > page_cgroup array into more arrays where each one is well kmalloc
> > aligned. This patch implements this idea. 
> 
> How about using alloc_pages_exact()?  These things aren't allocated
> often enough to really get most of the benefits of being in a slab.
> That'll at least get you down to a maximum of about PAGE_SIZE wasted.  
> 

yes, alloc_pages_exact() is much better.

packing page_cgroups for multiple sections causes breakage in memory hotplug logic.

Thanks,
-Kame

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