linux-kernel - Re: [PATCH 1/1] Memory usage limit notification addition to memcg

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Message-Id: <20090714100320.454ca54b.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 14 Jul 2009 10:03:20 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	"Vladislav D. Buzov" <vbuzov@...eddedalley.com>
Cc:	Paul Menage <menage@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Containers Mailing List 
	<containers@...ts.linux-foundation.org>,
	Dan Malek <dan@...eddedalley.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>
Subject: Re: [PATCH 1/1] Memory usage limit notification addition to memcg

On Mon, 13 Jul 2009 18:00:53 -0700
"Vladislav D. Buzov" <vbuzov@...eddedalley.com> wrote:

> Paul Menage wrote:
> > On Tue, Jul 7, 2009 at 5:56 PM, KAMEZAWA
> > Hiroyuki<kamezawa.hiroyu@...fujitsu.com> wrote:
> >   
> >> I know people likes to wait for file descriptor to get notification in these days.
> >> Can't we have "event" file descriptor in cgroup layer and make it reusable for
> >> other purposes ?
> >>     
> >
> > I agree - rather than having to add a separate "wait for value to
> > cross X threshold" file for each numeric usage value that people might
> > be concerned about, it would be better to have a generic way to do it
> > for any file. Given that this is a userspace API, it would be better
> > to work out at least the generic API first, even if the initial
> > implementation isn't generic.
> >  "OOM"
> >   
> We all agree on that. Our original intention was to create the memory
> limit notification capability, not a generic mechanism for the cgroup
> events. So, we started out with something that fits the current model.
> 
> > - independent thresholds for different waiters
> >   
> The threshold is one of the Memory Controller cgroup attributes, as well
> as memory usage limit. It is not a user task attribute and should not be
> controlled by user tasks. It's administrator or some control task job to
> set memory usage parameters within the cgroup. Once the threshold is
> reached, all tasks within the cgroup should be notified and do their
> best to free the memory.
> 
About this, I'll add following file.

  memory.reduce_usage  --- try to reduce memory usage to be smaller than...?

if your notifier goes in. Maybe good for dropping file caches etc.. for your notifer
use case.

Thanks,
-Kame





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