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Message-ID: <Pine.LNX.4.64.0701302225200.23658@chino.kir.corp.google.com> Date: Wed, 31 Jan 2007 07:18:09 -0800 (PST) From: David Rientjes <rientjes@...gle.com> To: Andrew Morton <akpm@...l.org> cc: Andi Kleen <ak@...e.de>, Rohit Seth <rohitseth@...gle.com>, linux-kernel@...r.kernel.org Subject: [patch -mm 4/7] 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@...e.de> Signed-off-by: David Rientjes <rientjes@...gle.com> --- 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 <rientjes@...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@...ads /]# mkdir exampleset + [root@...ads /]# mount -t cpuset none exampleset + [root@...ads /]# mkdir exampleset/ddset + [root@...ads /]# cd exampleset/ddset + [root@...ads /exampleset/ddset]# echo 0-1 > cpus + [root@...ads /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@...ads /exampleset/ddset]# echo $$ > tasks + [root@...ads /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. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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