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From: David Rientjes <>
To: Andrew Morton <>
Cc: Andi Kleen <>, Rohit Seth <>,
Subject: [patch -mm 5/5] x86_64: fake numa for cpusets document
Date: Thu, 25 Jan 2007 13:37:33 -0800 (PST)	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Create a document to explain how to use numa=fake in conjunction with
cpusets for coarse memory resource management.

An attempt to get more awareness and testing for this feature.

Cc: Andi Kleen <>
Signed-off-by: David Rientjes <>
 Documentation/x86_64/fake-numa-for-cpusets |   66 ++++++++++++++++++++++++++++
 1 files changed, 66 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/x86_64/fake-numa-for-cpusets

diff --git a/Documentation/x86_64/fake-numa-for-cpusets b/Documentation/x86_64/fake-numa-for-cpusets
new file mode 100644
index 0000000..d1a985c
--- /dev/null
+++ b/Documentation/x86_64/fake-numa-for-cpusets
@@ -0,0 +1,66 @@
+Using numa=fake and CPUSets for Resource Management
+Written by David Rientjes <>
+This document describes how the numa=fake x86_64 command-line option can be used
+in conjunction with cpusets for coarse memory management.  Using this feature,
+you can create fake NUMA nodes that represent contiguous chunks of memory and
+assign them to cpusets and their attached tasks.  This is a way of limiting the
+amount of system memory that are available to a certain class of tasks.
+For more information on the features of cpusets, see Documentation/cpusets.txt.
+There are a number of different configurations you can use for your needs.  For
+more information on the numa=fake command line option and its various ways of
+configuring fake nodes, see Documentation/x86_64/boot-options.txt.
+For the purposes of this introduction, we'll assume a very primitive NUMA
+emulation setup of "numa=fake=4*512,".  This will split our system memory into
+four equal chunks of 512M each that we can now use to assign to cpusets.  As
+you become more familiar with using this combination for resource control,
+you'll determine a better setup to minimize the number of nodes you have to deal
+A machine may be split as follows with "numa=fake=4*512," as reported by dmesg:
+	Faking node 0 at 0000000000000000-0000000020000000 (512MB)
+	Faking node 1 at 0000000020000000-0000000040000000 (512MB)
+	Faking node 2 at 0000000040000000-0000000060000000 (512MB)
+	Faking node 3 at 0000000060000000-0000000080000000 (512MB)
+	...
+	On node 0 totalpages: 130975
+	On node 1 totalpages: 131072
+	On node 2 totalpages: 131072
+	On node 3 totalpages: 131072
+Now following the instructions for mounting the cpusets filesystem from
+Documentation/cpusets.txt, you can assign fake nodes (i.e. contiguous memory
+address spaces) to individual cpusets:
+	[root@xroads /]# mkdir exampleset
+	[root@xroads /]# mount -t cpuset none exampleset
+	[root@xroads /]# mkdir exampleset/ddset
+	[root@xroads /]# cd exampleset/ddset
+	[root@xroads /exampleset/ddset]# echo 0-1 > cpus
+	[root@xroads /exampleset/ddset]# echo 0-1 > mems
+Now this cpuset, 'ddset', will only allowed access to fake nodes 0 and 1 for
+memory allocations (1G).
+You can now assign tasks to these cpusets to limit the memory resources
+available to them according to the fake nodes assigned as mems:
+	[root@xroads /exampleset/ddset]# echo $$ > tasks
+	[root@xroads /exampleset/ddset]# dd if=/dev/zero of=tmp bs=1024 count=1G
+	[1] 13425
+Notice the difference between the system memory usage as reported by
+/proc/meminfo between the restricted cpuset case above and the unrestricted
+case (i.e. running the same 'dd' command without assigning it to a fake NUMA
+				Unrestricted	Restricted
+	MemTotal:		3091900 kB	3091900 kB
+	MemFree:		  42113 kB	1513236 kB
+This allows for coarse memory management for the tasks you assign to particular
+cpusets.  Since cpusets can form a hierarchy, you can create some pretty
+interesting combinations of use-cases for various classes of tasks for your
+memory management needs.

  reply	other threads:[~2007-01-25 21:38 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-25 21:37 [patch -mm 1/5] x86_64: configurable fake numa node sizes David Rientjes
2007-01-25 21:37 ` [patch -mm 2/5] x86_64: split remaining fake nodes equally David Rientjes
2007-01-25 21:37   ` [patch -mm 3/5] x86_64: fixed-size remaining fake nodes David Rientjes
2007-01-25 21:37     ` [patch -mm 4/5] x86_64: fake numa function annotations David Rientjes
2007-01-25 21:37       ` David Rientjes [this message]
2007-01-29 13:36     ` [patch -mm 3/5] x86_64: fixed-size remaining fake nodes Andi Kleen
2007-01-29 18:38       ` David Rientjes
2007-01-30  1:19         ` David Rientjes

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