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SubjectRe: [RFC][PATCH 4/7][memcg] memcg use ID in page_cgroup
On Tue, Jul 27, 2010 at 04:56:29PM +0900, KAMEZAWA Hiroyuki wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> Now, addresses of memory cgroup can be calculated by their ID without complex.
> This patch relplaces pc->mem_cgroup from a pointer to a unsigned short.
> On 64bit architecture, this offers us more 6bytes room per page_cgroup.
> Use 2bytes for blkio-cgroup's page tracking. More 4bytes will be used for
> some light-weight concurrent access.
>
> We may able to move this id onto flags field but ...go step by step.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
> include/linux/page_cgroup.h | 3 ++-
> mm/memcontrol.c | 40 +++++++++++++++++++++++++---------------
> mm/page_cgroup.c | 2 +-
> 3 files changed, 28 insertions(+), 17 deletions(-)
>
> Index: mmotm-0719/include/linux/page_cgroup.h
> ===================================================================
> --- mmotm-0719.orig/include/linux/page_cgroup.h
> +++ mmotm-0719/include/linux/page_cgroup.h
> @@ -12,7 +12,8 @@
> */
> struct page_cgroup {
> unsigned long flags;
> - struct mem_cgroup *mem_cgroup;
> + unsigned short mem_cgroup; /* ID of assigned memory cgroup */
> + unsigned short blk_cgroup; /* Not Used..but will be. */

So later I shall have to use virtually indexed arrays in blkio controller?
Or you are just using virtually indexed arrays for lookup speed and
I can continue to use css_lookup() and not worry about using virtually
indexed arrays.

So the idea is that when a page is allocated, also store the blk_group
id and once that page is submitted for writeback, we should be able
to associate it to right blkio group?

Vivek


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