Re: [patch 1/3] mm: embed the memcg pointer directly into struct page
From: Konstantin Khlebnikov
Date: Thu Nov 06 2014 - 13:56:06 EST
On Sun, Nov 2, 2014 at 6:15 AM, Johannes Weiner <hannes@xxxxxxxxxxx> 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@xxxxxxxxxxx>
Great! Never thought I'd see this. =)
Acked-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
> ---
> include/linux/memcontrol.h | 6 +-
> include/linux/mm_types.h | 5 +
> include/linux/mmzone.h | 12 --
> include/linux/page_cgroup.h | 53 --------
> init/main.c | 7 -
> mm/memcontrol.c | 124 +++++------------
> mm/page_alloc.c | 2 -
> mm/page_cgroup.c | 319 --------------------------------------------
> 8 files changed, 41 insertions(+), 487 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index d4575a1d6e99..dafba59b31b4 100644
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