Re: [PATCH 1/2] memcg : update softlimit and threshold at commit.

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Fri, 12 Feb 2010 16:33:11 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Fri, 12 Feb 2010 15:47:13 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > Now, move_task introduced "batched" precharge. Because res_counter or css's refcnt
> > are not-scalable jobs for memcg, charge()s should be done in batched manner
> > if allowed.
> > 
> > Now, softlimit and threshold check their event counter in try_charge, but
> > this charge() is not per-page event. And event counter is not updated at charge().
> > Moreover, precharge doesn't pass "page" to try_charge() and softlimit tree
> > will be never updated until uncharge() causes an event.
> > 
> > So, the best place to check the event counter is commit_charge(). This is 
> > per-page event by its nature. This patch move checks to there.
> > 
> I agree to this direction.
> 
> > Cc: Kirill A. Shutemov <kirill@shutemov.name>
> > Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
> > Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> >  mm/memcontrol.c |   23 ++++++++++++-----------
> >  1 file changed, 12 insertions(+), 11 deletions(-)
> > 
> > Index: mmotm-2.6.33-Feb10/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-2.6.33-Feb10.orig/mm/memcontrol.c
> > +++ mmotm-2.6.33-Feb10/mm/memcontrol.c
> > @@ -1463,7 +1463,7 @@ static int __mem_cgroup_try_charge(struc
> >  		unsigned long flags = 0;
> >  
> >  		if (consume_stock(mem))
> > -			goto charged;
> > +			goto done;
> >  
> >  		ret = res_counter_charge(&mem->res, csize, &fail_res);
> >  		if (likely(!ret)) {
> > @@ -1558,16 +1558,7 @@ static int __mem_cgroup_try_charge(struc
> >  	}
> >  	if (csize > PAGE_SIZE)
> >  		refill_stock(mem, csize - PAGE_SIZE);
> > -charged:
> > -	/*
> > -	 * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
> > -	 * if they exceeds softlimit.
> > -	 */
> > -	if (page && mem_cgroup_soft_limit_check(mem))
> > -		mem_cgroup_update_tree(mem, page);
> >  done:
> > -	if (mem_cgroup_threshold_check(mem))
> > -		mem_cgroup_threshold(mem);
> >  	return 0;
> >  nomem:
> >  	css_put(&mem->css);
> After this change, @page can be removed from the arg of try_charge().
> 
Ah, hmm. good point. Will update.

Thanks,
-Kame


> 
> Thanks,
> Daisuke Nishimura.
> 
> > @@ -1691,6 +1682,16 @@ static void __mem_cgroup_commit_charge(s
> >  	mem_cgroup_charge_statistics(mem, pc, true);
> >  
> >  	unlock_page_cgroup(pc);
> > +	/*
> > +	 * "charge_statistics" updated event counter. Then, check it.
> > +	 * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
> > +	 * if they exceeds softlimit.
> > +	 */
> > +	if (mem_cgroup_soft_limit_check(mem))
> > +		mem_cgroup_update_tree(mem, pc->page);
> > +	if (mem_cgroup_threshold_check(mem))
> > +		mem_cgroup_threshold(mem);
> > +
> >  }
> >  
> >  /**
> > 
> > 
> 

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