Re: [patch 4/8] mm: memcg: lookup_page_cgroup (almost) never returns NULL

[Balbir Singh]

On Wed, Nov 23, 2011 at 9:12 PM, Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
> From: Johannes Weiner <jweiner@xxxxxxxxxx>
>
> Pages have their corresponding page_cgroup descriptors set up before
> they are used in userspace, and thus managed by a memory cgroup.
>
> The only time where lookup_page_cgroup() can return NULL is in the
> page sanity checking code that executes while feeding pages into the
> page allocator for the first time.
>

This is a legacy check from the days when we allocated PC during fault
time on demand. It might make sense to assert on !pc in DEBUG_VM mode
at some point in the future

Balbir
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