linux-kernel - Re: [PATCH mmotm 2.5/4] memcg: disable irq at page cgroup lock (Re: [PATCH -mmotm 3/4] memcg: dirty pages accounting and limiting infrastructure)

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Date:	Thu, 11 Mar 2010 13:58:47 +0900
From:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	balbir@...ux.vnet.ibm.com, linux-mm@...ck.org,
	Andrea Righi <arighi@...eler.com>,
	linux-kernel@...r.kernel.org,
	Trond Myklebust <trond.myklebust@....uio.no>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	containers@...ts.linux-foundation.org,
	Vivek Goyal <vgoyal@...hat.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [PATCH mmotm 2.5/4] memcg: disable irq at page cgroup lock (Re:
 [PATCH -mmotm 3/4] memcg: dirty pages accounting and limiting
 infrastructure)

On Thu, 11 Mar 2010 13:49:08 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> On Thu, 11 Mar 2010 13:31:23 +0900
> Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:
> 
> > On Wed, 10 Mar 2010 09:26:24 +0530, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> > > * nishimura@....nes.nec.co.jp <nishimura@....nes.nec.co.jp> [2010-03-10 10:43:09]:
> 
> > I made a patch(attached) using both local_irq_disable/enable and local_irq_save/restore.
> > local_irq_save/restore is used only in mem_cgroup_update_file_mapped.
> > 
> > And I attached a histogram graph of 30 times kernel build in root cgroup for each.
> > 
> >   before_root: no irq operation(original)
> >   after_root: local_irq_disable/enable for all
> >   after2_root: local_irq_save/restore for all
> >   after3_root: mixed version(attached)
> > 
> > hmm, there seems to be a tendency that before < after < after3 < after2 ?
> > Should I replace save/restore version to mixed version ?
> > 
> 
> IMHO, starting from after2_root version is the easist.
> If there is a chance to call lock/unlock page_cgroup can be called in
> interrupt context, we _have to_ disable IRQ, anyway.
> And if we have to do this, I prefer migration_lock rather than this mixture.
> 
I see.

> BTW, how big your system is ? Balbir-san's concern is for bigger machines.
> But I'm not sure this change is affecte by the size of machines.
> I'm sorry I have no big machine, now.
> 
My test machine have 8CPUs, and I run all the test with "make -j8".
Sorry, I don't have easy access to huge machine either.

> I'll consider yet another fix for race in account migration if I can.
> 
me too.


Thanks,
Daisuke Nishimura.
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