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] [day] [month] [year] [list]

Date:	Fri, 12 Mar 2010 08:46:14 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	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
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 11:54:13 -0500
Vivek Goyal <vgoyal@...hat.com> wrote:

> On Thu, Mar 11, 2010 at 01:49:08PM +0900, KAMEZAWA Hiroyuki 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.
> > 
> > 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.
> 
> FWIW, I took andrea's patches (local_irq_save/restore solution) and
> compiled the kernel on 32 cores hyperthreaded (64 cpus) with make -j32
> in /dev/shm/. On this system, I can't see much difference.
> 
> I compiled the kernel 10 times and took average.
> 
> Without andrea's patches: 28.698 (seconds)
> With andrea's patches: 28.711 (seconds).
> Diff is .04%
> 
> This is all should be in root cgroup. Note, I have not mounted memory cgroup
> controller but it is compiled in. So I am assuming that root group
> accounting will still be taking place. Also assuming that it is not
> required to do actual IO to disk and /dev/shm is enough to see the results
> of local_irq_save()/restore.
> 

Thank you!. Hmm.then, irq_xxxx is not core of problem. The overhead problem
is using spinlock or not... 

Regards,
-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/