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

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Date:	Tue, 4 Nov 2014 17:36:39 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Michal Hocko <mhocko@...e.cz>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Tejun Heo <tj@...nel.org>, David Miller <davem@...emloft.net>,
	<linux-mm@...ck.org>, <cgroups@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [patch 1/3] mm: embed the memcg pointer directly into struct
 page

(2014/11/02 12:15), 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@...xchg.org>
> ---
>   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(-)
> 

Great! 
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

BTW, init/Kconfig comments shouldn't be updated ?
(I'm sorry if it has been updated since your latest fix.)




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