linux-kernel - Re: The performance and behaviour of the anti-fragmentation related patches

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Date:	Fri, 2 Mar 2007 11:34:12 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	mel@...net.ie, npiggin@...e.de, clameter@...r.sgi.com,
	mingo@...e.hu, jschopp@...tin.ibm.com, arjan@...radead.org,
	torvalds@...ux-foundation.org, mbligh@...igh.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: The performance and behaviour of the anti-fragmentation related
 patches

On Thu, 1 Mar 2007 16:09:15 -0800
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Thu, 1 Mar 2007 10:12:50 +0000
> mel@...net.ie (Mel Gorman) wrote:
> 
> > Any opinion on merging these patches into -mm
> > for wider testing?
> 
> I'm a little reluctant to make changes to -mm's core mm unless those
> changes are reasonably certain to be on track for mainline, so let's talk
> about that.
> 
> What worries me is memory hot-unplug and per-container RSS limits.  We
> don't know how we're going to do either of these yet, and it could well be
> that the anti-frag work significantly complexicates whatever we end up
> doing there.
> 
> For prioritisation purposes I'd judge that memory hot-unplug is of similar
> value to the antifrag work (because memory hot-unplug permits DIMM
> poweroff).

About memory-hot-unplug, I'm now writing a new patch-set for memory-unplug for
showing my overview and roadmap. I'm now debugging it. I think I will be able to
post them as RFC in a week.

At least, ZONE_MOVABLE(or something partitioning memory) is necessary for
memory-hot-unplug like DIMM-poweroff. (I'm now using my own ZONE_MOVABLE patch, but
It is O.K. to migrate to Mel's one if it's ready to be merged.)


> Our basic unit of memory management is the zone.  Right now, a zone maps
> onto some hardware-imposed thing.  But the zone-based MM works *well*.  I
> suspect that a good way to solve both per-container RSS and mem hotunplug
> is to split the zone concept away from its hardware limitations: create a
> "software zone" and a "hardware zone".  All the existing page allocator and
> reclaim code remains basically unchanged, and it operates on "software
> zones".  Each software zones always lies within a single hardware zone. 
> The software zones are resizeable.  For per-container RSS we give each
> container one (or perhaps multiple) resizeable software zones.
> 
> For memory hotunplug, some of the hardware zone's software zones are marked
> reclaimable and some are not; DIMMs which are wholly within reclaimable
> zones can be depopulated and powered off or removed.
> 
Hmm...software-zone seems attractive.
I remember someone posted pesuedo-zone(pzone) patch in past.

-Kame

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