Re: [PATCH 3/4] Per cgroup background reclaim.

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Tue, 30 Nov 2010 16:51:42 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
 
> > +		if (IS_ERR(thr))
> > +			printk(KERN_INFO "Failed to start kswapd on memcg %d\n",
> > +				0);
> > +		else
> > +			kswapd_p->kswapd_task = thr;
> > +	}
> 
> Hmm, ok, then, kswapd-for-memcg is created when someone go over watermark.
> Why this new kswapd will not exit() until memcg destroy ?
> 
> I think there are several approaches.
> 
>   1. create/destroy a thread at memcg create/destroy
>   2. create/destroy a thread at watermarks.
>   3. use thread pool for watermarks.
>   4. use workqueue for watermaks.
> 
> The good point of "1" is that we can control a-thread-for-kswapd by cpu
> controller but it will use some resource.
> The good point of "2" is that we can avoid unnecessary resource usage.
> 
> 3 and 4 is not very good, I think. 
> 
> I'd like to vote for "1"...I want to avoid "stealing" other container's cpu
> by bad application in a container uses up memory.
> 

One more point, one-thread-per-hierarchy is enough. So, please check
memory.use_hierarchy==1 or not at creating a thread.

Thanks,
-kame

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