linux-kernel - Re: [PATCH 2/7] memcg: mem_cgroup_shrink_node

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Date:	Fri, 23 Jul 2010 14:14:00 +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 2/7] memcg: mem_cgroup_shrink_node_zone() doesn't need sc.nodemask

> * KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> [2010-07-16 19:14:15]:
> 
> > Currently mem_cgroup_shrink_node_zone() call shrink_zone() directly.
> > thus it doesn't need to initialize sc.nodemask. shrink_zone() doesn't
> > use it at all.
> > 
> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> > ---
> >  include/linux/swap.h |    3 +--
> >  mm/memcontrol.c      |    3 +--
> >  mm/vmscan.c          |    8 ++------
> >  3 files changed, 4 insertions(+), 10 deletions(-)
> > 
> > diff --git a/include/linux/swap.h b/include/linux/swap.h
> > index ff4acea..bf4eb62 100644
> > --- a/include/linux/swap.h
> > +++ b/include/linux/swap.h
> > @@ -244,8 +244,7 @@ extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
> >  extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
> >  						gfp_t gfp_mask, bool noswap,
> >  						unsigned int swappiness,
> > -						struct zone *zone,
> > -						int nid);
> > +						struct zone *zone);
> >  extern int __isolate_lru_page(struct page *page, int mode, int file);
> >  extern unsigned long shrink_all_memory(unsigned long nr_pages);
> >  extern int vm_swappiness;
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index aba4310..01f38ff 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -1307,8 +1307,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
> >  		/* we use swappiness of local cgroup */
> >  		if (check_soft)
> >  			ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
> > -				noswap, get_swappiness(victim), zone,
> > -				zone->zone_pgdat->node_id);
> > +				noswap, get_swappiness(victim), zone);
> >  		else
> >  			ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
> >  						noswap, get_swappiness(victim));
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index bd1d035..be860a0 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1929,7 +1929,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
> >  unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
> >  						gfp_t gfp_mask, bool noswap,
> >  						unsigned int swappiness,
> > -						struct zone *zone, int nid)
> > +						struct zone *zone)
> >  {
> >  	struct scan_control sc = {
> >  		.nr_to_reclaim = SWAP_CLUSTER_MAX,
> > @@ -1940,13 +1940,9 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
> >  		.order = 0,
> >  		.mem_cgroup = mem,
> >  	};
> > -	nodemask_t nm  = nodemask_of_node(nid);
> > -
> >  	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
> >  			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
> > -	sc.nodemask = &nm;
> > -	sc.nr_reclaimed = 0;
> > -	sc.nr_scanned = 0;
> 
> We need the initialization to 0, is there a reason why it was removed?

please reread C spec and other scan_control user.
sc_nr_* were already initialized in struct scan_control sc = { } line.



> What happens when we compare or increment sc.nr_*?
> 
> Can we keep this indepedent of the tracing patches?
> 
> > +
> >  	/*
> >  	 * NOTE: Although we can get the priority field, using it
> >  	 * here is not a good idea, since it limits the pages we can scan.
> > -- 
> > 1.6.5.2
> > 
> > 
> > 
> > --
> > To unsubscribe, send a message with 'unsubscribe linux-mm' in
> > the body to majordomo@...ck.org.  For more info on Linux MM,
> > see: http://www.linux-mm.org/ .
> > Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
> 
> -- 
> 	Three Cheers,
> 	Balbir



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