linux-kernel - Re: [PATCH 1/7] memcg: sc.nr_to

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Date:	Fri, 23 Jul 2010 16:33:13 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	kosaki.motohiro@...fujitsu.com,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Nishimura Daisuke <d-nishimura@....biglobe.ne.jp>
Subject: Re: [PATCH 1/7] memcg: sc.nr_to_reclaim should be initialized

> * KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> [2010-07-16 19:13:31]:
> 
> > Currently, mem_cgroup_shrink_node_zone() initialize sc.nr_to_reclaim as 0.
> > It mean shrink_zone() only scan 32 pages and immediately return even if
> > it doesn't reclaim any pages.
> > 
> > This patch fixes it.
> > 
> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> > ---
> >  mm/vmscan.c |    1 +
> >  1 files changed, 1 insertions(+), 0 deletions(-)
> > 
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 1691ad0..bd1d035 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1932,6 +1932,7 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
> >  						struct zone *zone, int nid)
> >  {
> >  	struct scan_control sc = {
> > +		.nr_to_reclaim = SWAP_CLUSTER_MAX,
> >  		.may_writepage = !laptop_mode,
> >  		.may_unmap = 1,
> >  		.may_swap = !noswap,
> 
> Could you please do some additional testing on
> 
> 1. How far does this push pages (in terms of when limit is hit)?

32 pages per mem_cgroup_shrink_node_zone().

That said, the algorithm is here.

1. call mem_cgroup_largest_soft_limit_node()
   calculate largest cgroup
2. call mem_cgroup_shrink_node_zone() and shrink 32 pages
3. goto 1 if limit is still exceed.

If it's not your intention, can you please your intended algorithm?


> 2. Did you hit a problem with the current setting or is it a review
> fix?

I've found this by review. and my patch works fine on my test environment.
Of cource, if you do _not_ run the code on heavy pressure, your original code
works too.


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