Re: [PATCH] top level scheduler domain for ia64

From: Takayoshi Kochi <>
Date: 2004-11-03 17:15:47

From: "Luck, Tony" <>
Subject: RE: [PATCH] top level scheduler domain for ia64
Date: Tue, 2 Nov 2004 13:31:16 -0800

> >> I think the short-term solution is to make the boot-time parameter
> >> like Jesse said to control the creation and span size of the
> >> node domain and see what is necessary next.
> >
> >This patch adds a new kernel parameter "nodes_per_domain"
> >which specifies how many nodes are included in a node 
> >scheduling domain.
> Can you add a short write-up for Documentation/kernel-parameters.txt
> to explain the effect, and how a user should pick what value to use
> (examples would be good ... if SGI want to throw in some
> values for small/large Altix boxes, that would be good too).

The diff is attached.
Though I'm not sure how to pick the best number...
Any ideas from SGI?

> Is '6' a reasonable default if the parameter is not set?

Maybe for Altix.  I guess the only user of this domain split
is Altix, so it's ok ;)

The patch below is a documentation for 'nodes_per_domain=' option.

Signed-off-by: Takayoshi Kochi <>

===== my-bk/Documentation/kernel-parameters.txt 1.57 vs edited =====
--- 1.57/Documentation/kernel-parameters.txt	2004-10-30 18:31:21 +09:00
+++ edited/my-bk/Documentation/kernel-parameters.txt	2004-11-03 15:07:20 +09:00
@@ -475,6 +475,15 @@
 	hugepages=	[HW,IA-32,IA-64] Maximal number of HugeTLB pages.
+	nodes_per_domain=n
+			[IA-64] specifies number of nodes in a scheduling
+			domain.  If the number of nodes in a sysmtem is
+			large enough, the node scheduling domain (usually
+			spans the whole system) is split into <n> nodes
+			for each.  Default <n> is 6.
+			If you have a large NUMA machine, consider using
+			this option to reduce load balancing overhead.
 	noirqbalance	[IA-32,SMP,KNL] Disable kernel irq balancing	[HW] Put keyboard port into non-translated mode

Takayoshi Kochi
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Received on Wed Nov 3 01:16:14 2004

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