linux-kernel - Re: [patch 7/8] vmscan: memcg-aware unevictable page rescue scanner

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Date:	Mon, 29 Aug 2011 09:59:41 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Ying Han <yinghan@...gle.com>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Greg Thelen <gthelen@...gle.com>,
	Michel Lespinasse <walken@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>
Subject: Re: [patch 7/8] vmscan: memcg-aware unevictable page rescue scanner

On Mon, Aug 29, 2011 at 12:28:22AM -0700, Ying Han wrote:
> On Tue, Jul 19, 2011 at 5:36 PM, Johannes Weiner <hannes@...xchg.org> wrote:
> > On Tue, Jul 19, 2011 at 03:47:43PM -0700, Ying Han wrote:
> >> On Tue, May 31, 2011 at 11:25 PM, Johannes Weiner <hannes@...xchg.org>wrote:
> >>
> >> > Once the per-memcg lru lists are exclusive, the unevictable page
> >> > rescue scanner can no longer work on the global zone lru lists.
> >> >
> >> > This converts it to go through all memcgs and scan their respective
> >> > unevictable lists instead.
> >> >
> >> > Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> >> > ---
> >> >  include/linux/memcontrol.h |    2 +
> >> >  mm/memcontrol.c            |   11 +++++++++
> >> >  mm/vmscan.c                |   53
> >> > +++++++++++++++++++++++++++----------------
> >> >  3 files changed, 46 insertions(+), 20 deletions(-)
> >> >
> >> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> >> > index cb02c00..56c1def 100644
> >> > --- a/include/linux/memcontrol.h
> >> > +++ b/include/linux/memcontrol.h
> >> > @@ -60,6 +60,8 @@ extern void mem_cgroup_cancel_charge_swapin(struct
> >> > mem_cgroup *ptr);
> >> >
> >> >  extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct
> >> > *mm,
> >> >                                        gfp_t gfp_mask);
> >> > +struct page *mem_cgroup_lru_to_page(struct zone *, struct mem_cgroup *,
> >> > +                                   enum lru_list);
> >> >
> >>
> >> Did we miss a #ifdef case for this function? I got compile error by
> >> disabling memcg.
> >
> > I assume it's because the call to it is not optimized away properly in
> > the disabled case.  I'll have it fixed in the next round, thanks for
> > letting me know.
> >
> 
> Hi Johannes:
> 
> This is the change for the hierarchy_walk() sent on the other patch,
> also including a fix. Please consider to fold in your patch:
> 
> Fix the hierarchy_walk() in the unevictable page rescue scanner
> 
> the patch including changes
> 1. adjust the change in hierarchy_walk() which needs to hold the reference to
> the first mem_cgroup.
> 2. add stop_hierarchy_walk() at the end which is missed on the original patch.
> 
> Signed-off-by: Ying Han <yinghan@...gle.com>
> 
> Change-Id: I72fb5d351faf0f111c8c99edd90b6cfee6281d3f
> ---
>  mm/memcontrol.c |    3 +++
>  mm/vmscan.c     |    7 ++++---
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 9bcd429..426092b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1514,6 +1514,9 @@ void mem_cgroup_stop_hierarchy_walk(struct
> mem_cgroup *target,
>  >------>------->------->-------    struct mem_cgroup *first,
>  >------>------->------->-------    struct mem_cgroup *mem)
>  {
> +>------if (!target)
> +>------>-------target = root_mem_cgroup;

This is important and I have it already in my tree.

After the changes to the iteration process as explained in my previous
email, I don't think the rest of this patch is necessary.  Can you
confirm?  Thanks!
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