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author | David Rientjes <rientjes@google.com> | 2007-05-02 19:27:09 +0200 |
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committer | Andi Kleen <andi@basil.nowhere.org> | 2007-05-02 19:27:09 +0200 |
commit | 20280195f2a3d80c42a190959ca22108c93cd7e0 (patch) | |
tree | 5cfb384cf22c94f854a3a58acdb2b5341361e8bc /Documentation/x86_64 | |
parent | d824395c5994adbf7efe377cc67f732133270554 (diff) | |
download | op-kernel-dev-20280195f2a3d80c42a190959ca22108c93cd7e0.zip op-kernel-dev-20280195f2a3d80c42a190959ca22108c93cd7e0.tar.gz |
[PATCH] x86-64: fake numa for cpusets document
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 <ak@suse.de>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Paul Jackson <pj@sgi.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'Documentation/x86_64')
-rw-r--r-- | Documentation/x86_64/fake-numa-for-cpusets | 66 |
1 files changed, 66 insertions, 0 deletions
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 <rientjes@cs.washington.edu> + +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 +with. + +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 +cpuset): + 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. |