[Devel] Re: [PATCH v5 07/14] mm: Allocate kernel pages to the right memcg

[Andrew Morton]

On Tue, 16 Oct 2012 14:16:44 +0400
Glauber Costa <glommer at parallels.com> 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.