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)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20100311134908.48d8b0fc.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 11 Mar 2010 13:49:08 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
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>
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 13:31:23 +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.

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.

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

Thanks,
-Kame


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/