Re: [RFC PATCH] page_cgroup: Reduce allocation overhead forpage_cgroup array for CONFIG_SPARSEMEM
From: KAMEZAWA Hiroyuki
Date: Thu Feb 24 2011 - 05:09:12 EST
On Thu, 24 Feb 2011 10:35:19 +0100
Michal Hocko <mhocko@xxxxxxx> wrote:
> On Thu 24-02-11 08:52:27, KAMEZAWA Hiroyuki wrote:
> > 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.
> I am not sure I understand this. What do you mean by packing
> page_cgroups for multiple sections? The patch I have posted doesn't do
> any packing. Or do you mean that using a double array can break hotplog?
> Not that this would change anything, alloc_pages_exact is really a
> better solution, I am just curious ;)
Sorry, it seems I failed to read code correctly.
You just implemented 2 level table..
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