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SubjectRe: [PATCH] memcg: remove PCG_CACHE page_cgroup flag
On Thu 19-01-12 18:17:11, KAMEZAWA Hiroyuki wrote:
> This patch is onto memcg-devel, can be applied to linux-next, too.

Just for record memcg-devel tree should _always_ be compatible with
linux-next. It just contains patches which are memcg related to be more
stable for memcg specific development.

>
> ==
> From 529653c266b0682894d64e4797fcaf6a3c35db25 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Date: Thu, 19 Jan 2012 17:09:41 +0900
> Subject: [PATCH] memcg: remove PCG_CACHE
>
> We record 'the page is cache' by PCG_CACHE bit to page_cgroup.
> Here, "CACHE" means anonymous user pages (and SwapCache). This
> doesn't include shmem.

> Consdering callers, at charge/uncharge, the caller should know
> what the page is and we don't need to record it by using 1bit
> per page.
>
> This patch removes PCG_CACHE bit and make callers of
> mem_cgroup_charge_statistics() to specify what the page is.
>
> Changelog since RFC.
> - rebased onto memcg-devel
> - rename 'file' to 'not_rss'

The name is confusing.

Other than that the patch looks reasonable. Minor comment bellow:

> - some cleanup and added comment.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
> include/linux/page_cgroup.h | 8 +-----
> mm/memcontrol.c | 55 ++++++++++++++++++++++++++----------------
> 2 files changed, 35 insertions(+), 28 deletions(-)
>
[...]
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index fb2dfc3..de7721d 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
[...]
> @@ -2908,9 +2915,15 @@ void mem_cgroup_uncharge_page(struct page *page)
>
> void mem_cgroup_uncharge_cache_page(struct page *page)
> {
> + int ctype;
> +
> VM_BUG_ON(page_mapped(page));
> VM_BUG_ON(page->mapping);
> - __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE);
> + if (page_is_file_cache(page))
> + ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
> + else
> + ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
> + __mem_cgroup_uncharge_common(page, ctype);

OK, this makes sense but doesn't make any real difference now, so it is
more a clean up, right?

Thanks
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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