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From: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
To: Christoph Lameter <clameter@sgi.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH] change global zonelist order v4 [0/2]
Date: Fri, 04 May 2007 13:24:19 -0400	[thread overview]
Message-ID: <1178299460.5236.35.camel@localhost> (raw)
In-Reply-To: <Pine.LNX.4.64.0705040913340.21436@schroedinger.engr.sgi.com>

On Fri, 2007-05-04 at 09:18 -0700, Christoph Lameter wrote:
> On Fri, 4 May 2007, Jesse Barnes wrote:
> 
> > I think the idea is to avoid exhausting ZONE_DMA on some NUMA boxes by 
> > ordering the fallback list first by zone, then by node distance (e.g. 
> > ZONE_NORMAL of local node, then ZONE_NORMAL of next nearest node etc., 
> > followed by ZONE_DMA of local node, ZONE_DMA of next nearest node, etc.).
> 
> Maybe it would be cleaner to setup a DMA and DMA32 "node" up and define 
> them at a certain distance to the rest of the nodes that only contain 
> ZONE_NORMAL (or the zone that is replicated on all nodes). Then we would 
> have that effect without reworking zone list generation. Plus in the long 
> run we may then be able to get to 1 zone per node avoiding the 
> difficulties coming zone fallback altogether.
> 
> > Another option would be to make this behavior automatic if both ZONE_DMA 
> > and ZONE_NORMAL had pages.  I initially wrote this stuff with the idea 
> > that machines that really needed it would have all their memory in 
> > ZONE_DMA, but obviously that's not the case, so some more smarts are 
> > needed.
> 
> I think what would work is to first setup nodes that use the highest zone. 
> Then add virtual nodes for the lower zones that may only exist on a single 
> node.
> 
> I.e. a 4 node x86_64 box may have
> 
> Node
> 0	ZONE_NORMAL
> 1	ZONE_NORMAL
> 2	ZONE_NORMAL
> 3	ZONE_NORMAL
> 4	ZONE_DMA32
> 5	[additional ZONE_DMA32 if zone DMA32 is split over multiple nodes]
> 6	ZONE_DMA
> 
> The SLIT information can be used to control how the nodes fallback to the 
> DMA32 nodes on 4 and 5. Node 6 would be given a very high SLIT distance so 
> that it would be used only if an actual __GFP_DMA occurs or the system 
> really runs into memory difficulties.

Hmmm...  "serious hackery", indeed!  ;-)

Lee


  reply	other threads:[~2007-05-04 17:24 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-04-27  5:45 KAMEZAWA Hiroyuki
2007-04-27  6:04 ` [PATCH] change global zonelist order v4 [1/2] change zonelist ordering KAMEZAWA Hiroyuki
2007-04-30 16:12   ` Lee Schermerhorn
2007-04-27  6:17 ` [PATCH] change global zonelist order v4 [2/2] auto configuration KAMEZAWA Hiroyuki
2007-04-30 16:26   ` Lee Schermerhorn
2007-05-04  5:47 ` [PATCH] change global zonelist order v4 [0/2] Andrew Morton
2007-05-04 15:26   ` Jesse Barnes
2007-05-04 16:18     ` Christoph Lameter
2007-05-04 17:24       ` Lee Schermerhorn [this message]
2007-05-04 17:28         ` Christoph Lameter
2007-05-04 17:36           ` Jesse Barnes
2007-05-04 18:03             ` Christoph Lameter
2007-05-04 17:12   ` Lee Schermerhorn

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