linux-kernel - Re: [RFC] Shared page accounting for memory cgroup

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Date:	Wed, 6 Jan 2010 16:12:11 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>
Subject: Re: [RFC] Shared page accounting for memory cgroup

On Wed, 6 Jan 2010 12:31:50 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> > No. If it takes long time, locking fork()/exit() for such long time is the bigger
> > issue.
> > I recommend you to add memacct subsystem to sum up RSS of all processes's RSS counting
> > under a cgroup.  Althoght it may add huge costs in page fault path but implementation
> > will be very simple and will not hurt realtime ops.
> > There will be no terrible race, I guess.
> >
> 
> But others hold that lock as well, simple thing like listing tasks and
> moving tasks, etc. I expect the usage of shared to be in the same
> range.
> 

And piles up costs ? I think cgroup guys should pay attention to fork/exit
costs more. Now, it gets slower and slower.
In that point, I never like migrate-at-task-move work in cpuset and memcg.

My 1st objection to this patch is this "shared" doesn't mean "shared between
cgroup" but means "shared between processes".
I think it's of no use and no help to users.

And implementation is 2nd thing.


Thanks,
-Kame

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