Re: [RFC][PATCH] syctl for selecting global zonelist[] order

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

On Wed, 25 Apr 2007 12:17:15 -0700 (PDT)
Christoph Lameter <clameter@sgi.com> wrote:

> On Wed, 25 Apr 2007, KAMEZAWA Hiroyuki wrote:
> 
> > Make zonelist policy selectable from sysctl.
> > 
> > Assume 2 node NUMA, only node(0) has ZONE_DMA (ZONE_DMA32).
> > 
> > In this case, default (node0's) zonelist order is
> > 
> > Node(0)'s NORMAL -> Node(0)'s DMA -> Node(1)"s NORMAL.
> > 
> > This means Node(0)'s DMA is used before Node(1)'s NORMAL.
> 
> So a IA64 platform with i386 sicknesses? And pretty bad case of it since I 
> assume that the memory sizes per node are equal. Your solution of taking 
> 4G off node 0 and then going to node 1 first must hurt some 
> processes running on node 0. 
I think so, too. It is because I made this as selectable option.

> Whatever you do the  memory balance between the two nodes is making
> the system behave in an unsymmetric way.


> > In some server, some application uses large memory allcation.
> > This exhaust memory in the above order.
> 
> Could we add a boot time option instead that changes the zonelist build 
> behavior? Maybe an arch hook that can deal with it?
> 
Yes, it' in my plan. I'll add boot option support.

Thanks,
-Kame

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