linux-kernel - Re: [PATCH 3/3] Provide control over unmapped pages (v4)

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Message-Id: <20110131085853.b09aef2d.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Mon, 31 Jan 2011 08:58:53 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Minchan Kim <minchan.kim@...il.com>, balbir@...ux.vnet.ibm.com,
	linux-mm@...ck.org, akpm@...ux-foundation.org, npiggin@...nel.dk,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	kosaki.motohiro@...fujitsu.com
Subject: Re: [PATCH 3/3] Provide control over unmapped pages (v4)

On Fri, 28 Jan 2011 09:20:02 -0600 (CST)
Christoph Lameter <cl@...ux.com> wrote:

> On Fri, 28 Jan 2011, KAMEZAWA Hiroyuki wrote:
> 
> > > > I see it as a tradeoff of when to check? add_to_page_cache or when we
> > > > are want more free memory (due to allocation). It is OK to wakeup
> > > > kswapd while allocating memory, somehow for this purpose (global page
> > > > cache), add_to_page_cache or add_to_page_cache_locked does not seem
> > > > the right place to hook into. I'd be open to comments/suggestions
> > > > though from others as well.
> >
> > I don't like add hook here.
> > AND I don't want to run kswapd because 'kswapd' has been a sign as
> > there are memory shortage. (reusing code is ok.)
> >
> > How about adding new daemon ? Recently, khugepaged, ksmd works for
> > managing memory. Adding one more daemon for special purpose is not
> > very bad, I think. Then, you can do
> >  - wake up without hook
> >  - throttle its work.
> >  - balance the whole system rather than zone.
> >    I think per-node balance is enough...
> 
> 
> I think we already have enough kernel daemons floating around. They are
> multiplying in an amazing way. What would be useful is to map all
> the memory management background stuff into a process. May call this memd
> instead? Perhaps we can fold khugepaged into kswapd as well etc.
> 

Making kswapd slow for whis "additional", "requested by user, not by system"
work is good thing ? I think workqueue works enough well, it's scale based on
workloads, if using thread is bad.

Thanks,
-Kame




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