linux-kernel - Re: [patch 08/11] mm: memcg: remove needless !mm fixup to init

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Date:	Tue, 10 Jul 2012 08:21:04 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Wanpeng Li <liwp.linux@...il.com>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 08/11] mm: memcg: remove needless !mm fixup to init_mm
 when charging

On Tue 10-07-12 14:10:21, Wanpeng Li wrote:
> On Mon, Jul 09, 2012 at 05:20:58PM +0200, Michal Hocko wrote:
> >On Thu 05-07-12 02:45:00, Johannes Weiner wrote:
> >> It does not matter to __mem_cgroup_try_charge() if the passed mm is
> >> NULL or init_mm, it will charge the root memcg in either case.
> 
> You can also change the comment in __mem_cgroup_try_charge :
> 
> "if so charge the init_mm" => "if so charge the root memcg"

This is already in place:
"
If mm is NULL and the caller doesn't pass a valid memcg pointer, that is
treated as a charge to root_mem_cgroup.
"
> 
> >> 
> >> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> >
> >Acked-by: Michal Hocko <mhocko@...e.cz>
> >
> >> ---
> >>  mm/memcontrol.c |    5 -----
> >>  1 files changed, 0 insertions(+), 5 deletions(-)
> >> 
> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >> index 418b47d..6fe4101 100644
> >> --- a/mm/memcontrol.c
> >> +++ b/mm/memcontrol.c
> >> @@ -2766,8 +2766,6 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
> >>  		ret = 0;
> >>  	return ret;
> >>  charge_cur_mm:
> >> -	if (unlikely(!mm))
> >> -		mm = &init_mm;
> >>  	ret = __mem_cgroup_try_charge(mm, mask, 1, memcgp, true);
> >>  	if (ret == -EINTR)
> >>  		ret = 0;
> >> @@ -2832,9 +2830,6 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
> >>  	if (PageCompound(page))
> >>  		return 0;
> >>  
> >> -	if (unlikely(!mm))
> >> -		mm = &init_mm;
> >> -
> >>  	if (!PageSwapCache(page))
> >>  		ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
> >>  	else { /* page is swapcache/shmem */
> >> -- 
> >> 1.7.7.6
> >> 
> >
> >-- 
> >Michal Hocko
> >SUSE Labs
> >SUSE LINUX s.r.o.
> >Lihovarska 1060/12
> >190 00 Praha 9    
> >Czech Republic
> >--
> >To unsubscribe from this list: send the line "unsubscribe cgroups" in
> >the body of a message to majordomo@...r.kernel.org
> >More majordomo info at  http://vger.kernel.org/majordomo-info.html

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