Re: [patch 1/3] mm: embed the memcg pointer directly into struct page

[Vladimir Davydov <vdavydov@parallels.com>]

On Sat, Nov 01, 2014 at 11:15:54PM -0400, Johannes Weiner wrote:
> Memory cgroups used to have 5 per-page pointers.  To allow users to
> disable that amount of overhead during runtime, those pointers were
> allocated in a separate array, with a translation layer between them
> and struct page.
> 
> There is now only one page pointer remaining: the memcg pointer, that
> indicates which cgroup the page is associated with when charged.  The
> complexity of runtime allocation and the runtime translation overhead
> is no longer justified to save that *potential* 0.19% of memory.  With
> CONFIG_SLUB, page->mem_cgroup actually sits in the doubleword padding
> after the page->private member and doesn't even increase struct page,
> and then this patch actually saves space.  Remaining users that care
> can still compile their kernels without CONFIG_MEMCG.
> 
>    text    data     bss     dec     hex     filename
> 8828345 1725264  983040 11536649 b00909  vmlinux.old
> 8827425 1725264  966656 11519345 afc571  vmlinux.new
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: Vladimir Davydov <vdavydov@parallels.com>

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