linux-kernel - Re: [RFC][PATCH] memcg soft limit (yet another new design) v1

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Message-ID: <20090331061010.GJ16497@balbir.in.ibm.com>
Date:	Tue, 31 Mar 2009 11:40:10 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>
Subject: Re: [RFC][PATCH] memcg soft limit (yet another new design) v1

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-03-31 14:05:02]:

> On Tue, 31 Mar 2009 10:30:55 +0530
> Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> 
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-03-31 08:55:38]:
> > 
> > > On Sat, 28 Mar 2009 23:57:47 +0530
> > > Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> > > 
> > > > * Balbir Singh <balbir@...ux.vnet.ibm.com> [2009-03-28 23:41:00]:
> > > > 
> > > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-03-27 13:59:33]:
> > > > > 
> > > > > > ==brief test result==
> > > > > > On 2CPU/1.6GB bytes machine. create group A and B
> > > > > >   A.  soft limit=300M
> > > > > >   B.  no soft limit
> > > > > > 
> > > > > >   Run a malloc() program on B and allcoate 1G of memory. The program just
> > > > > >   sleeps after allocating memory and no memory refernce after it.
> > > > > >   Run make -j 6 and compile the kernel.
> > > > > > 
> > > > > >   When vm.swappiness = 60  => 60MB of memory are swapped out from B.
> > > > > >   When vm.swappiness = 10  => 1MB of memory are swapped out from B    
> > > > > > 
> > > > > >   If no soft limit, 350MB of swap out will happen from B.(swapiness=60)
> > > > > >
> > > > > 
> > > > > I ran the same tests, booted the machine with mem=1700M and maxcpus=2
> > > > > 
> > > > > Here is what I see with
> > > > 
> > > > I meant to say, Here is what I see with my patches (v7)
> > > > 
> > > Hmm, I saw 250MB of swap out ;) As I reported before.
> > 
> > Swapout for A? For A it is expected, but for B it is not. How many
> > nodes do you have on your machine? Any fake numa nodes?
> > 
> Of course, from B.
>

I asked because I see A have a swapout of 350 MB, which is expected
since it is way over its soft limit.
 
> Nothing special boot options. My test was on VMware 2cpus/1.6GB memory.
> 
> I wonder why swapout can be 0 on your test. Do you add some extra hooks to
> kswapd ?
>

Nope.. no special hooks to kswapd. B never enters the RB-Tree and thus
never hits the memcg soft limit reclaim path. kswapd can reclaim from
it, but it grows back quickly. At some point, memcg soft limit reclaim
hits A and reclaims memory from it, allowing B to run without any
problems. I am talking about the state at the end of the experiment.

 

-- 
	Balbir
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