On Tue, 16 Oct 2012 14:16:44 +0400
Glauber Costa [off-list ref] wrote:

When a process tries to allocate a page with the __GFP_KMEMCG flag, the
page allocator will call the corresponding memcg functions to validate
the allocation. Tasks in the root memcg can always proceed.

To avoid adding markers to the page - and a kmem flag that would
necessarily follow, as much as doing page_cgroup lookups for no reason,
whoever is marking its allocations with __GFP_KMEMCG flag is responsible
for telling the page allocator that this is such an allocation at
free_pages() time.

Well, why?  Was that the correct decision?

This is done by the invocation of
__free_accounted_pages() and free_accounted_pages().

These are very general-sounding names.  I'd expect the identifiers to
contain "memcg" and/or "kmem", to identify what's going on.

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