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Date: Thu, 31 Mar 2011 22:16:51 +0800 From: "Zhang, Yang Z" <yang.z.zhang@...el.com> To: "akpm@...ux-foundation.org" <akpm@...ux-foundation.org> CC: "linux-mm@...ck.org" <linux-mm@...ck.org>, "haicheng.li@...ux.intel.com" <haicheng.li@...ux.intel.com>, "lethal@...ux-sh.org" <lethal@...ux-sh.org>, "Kleen, Andi" <andi.kleen@...el.com>, "dave@...ux.vnet.ibm.com" <dave@...ux.vnet.ibm.com>, "gregkh@...e.de" <gregkh@...e.de>, "mingo@...e.hu" <mingo@...e.hu>, "lenb@...nel.org" <lenb@...nel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "yinghai@...nel.org" <yinghai@...nel.org>, "Li, Xin" <xin.li@...el.com> Subject: [PATCH 1/7,v10] NUMA Hotplug Emulator: Documentation add a text file Documentation/x86/x86_64/numa_hotplug_emulator.txt to explain the usage for the hotplug emulator. Reviewed-By: Randy Dunlap <randy.dunlap@...cle.com> Signed-off-by: David Rientjes <rientjes@...gle.com> Signed-off-by: Haicheng Li <haicheng.li@...el.com> Signed-off-by: Shaohui Zheng <shaohui.zheng@...el.com> Signed-off-by: Yang Zhang <yang.z.zhang@...el.com> --- Documentation/x86/x86_64/numa_hotplug_emulator.txt | 102 ++++++++++++++++++++ 1 files changed, 102 insertions(+), 0 deletions(-) create mode 100644 Documentation/x86/x86_64/numa_hotplug_emulator.txt diff --git a/Documentation/x86/x86_64/numa_hotplug_emulator.txt linux-hpe4/Documentation/x86/x86_64/numa_hotplug_emulator.txt new file mode 100644 index 0000000..ca7cc42 --- /dev/null +++ linux-hpe4/Documentation/x86/x86_64/numa_hotplug_emulator.txt @@ -0,0 +1,102 @@ +NUMA Hotplug Emulator for x86_64 +--------------------------------------------------- + +NUMA hotplug emulator is able to emulate NUMA Node Hotplug +thru a pure software way. It intends to help people easily debug +and test node/CPU/memory hotplug related stuff on a +none-NUMA-hotplug-support machine, even a UMA machine and virtual +environment. + +1) Node hotplug emulation: + +Adds a numa=possible=<N> command line option to set an additional N nodes +as being possible for memory hotplug. This set of possible nodes +control nr_node_ids and the sizes of several dynamically allocated node +arrays. + +This allows memory hotplug to create new nodes for newly added memory +rather than binding it to existing nodes. + +For emulation on x86, it would be possible to set aside memory for hotplugged +nodes (say, anything above 2G) and to add an additional four nodes as being +possible on boot with + + mem=2G numa=possible=4 + +and then creating a new 128M node at runtime: + + # echo 128M@...0000000 > /sys/kernel/debug/node_hotplug/add_node + On node 1 totalpages: 0 + init_memory_mapping: 0000000080000000-0000000088000000 + 0080000000 - 0088000000 page 2M + +Once the new node has been added, its memory can be onlined. If this +memory represents memory section 16, for example: + + # echo online > /sys/devices/system/memory/memory16/state + Built 2 zonelists in Node order, mobility grouping on. Total pages: 514846 + Policy zone: Normal + [ The memory section(s) mapped to a particular node are visible via + /sys/devices/system/mem_hotplug/node1, in this example. ] + +2) CPU hotplug emulation: + +The emulator reserves CPUs thru grub parameter, the reserved CPUs can be +hot-add/hot-remove in software method, it emulates the process of physical +cpu hotplug. + +When hotplugging a CPU with emulator, we are using a logical CPU to emulate the +CPU socket hotplug process. For the CPU supported SMT, some logical CPUs are in +the same socket, but it may located in different NUMA node after we have +emulator. We put the logical CPU into a fake CPU socket, and assign it a +unique phys_proc_id. For the fake socket, we put one logical CPU in only. + + - to hide CPUs + - Using boot option "maxcpus=N" hide CPUs + N is the number of CPUs to initialize; the reset will be hidden. + - Using boot option "cpu_hpe=on" to enable CPU hotplug emulation + when cpu_hpe is enabled, the rest CPUs will not be initialized + + - to hot-add CPU to node + # echo node_id > /sys/devices/system/cpu/probe + + - to hot-remove CPU + # echo cpu_id > /sys/devices/system/cpu/release + +3) Memory hotplug emulation: + +The emulator reserves memory before OS boots, the reserved memory region is +removed from e820 table. Each online node has an add_memory interface, and +memory can be hot-added via the per-ndoe add_memory debugfs interface. + +The difficulty of Memory Release is well-known, we have no plan for it until +now. + + - reserve memory thru a kernel boot paramter + mem=1024m + + - add a memory section to node 3 + # echo 0x40000000 > /sys/kernel/debug/node_hotplug/node3/add_memory + OR + # echo 1024m > /sys/kernel/debug/node_hotplug/node3/add_memory + +4) Script for hotplug testing + +These scripts provides convenience when we hot-add memory/cpu in batch. + +- Online all memory sections: +for m in /sys/devices/system/memory/memory*; +do + echo online > $m/state; +done + +- CPU Online: +for c in /sys/devices/system/cpu/cpu*; +do + echo 1 > $c/online; +done + +- David Rientjes <rientjes@...gle.com> +- Haicheng Li <haicheng.li@...el.com> +- Shaohui Zheng <shaohui.zheng@...el.com> +- Yang Zhang <yang.z.zhang@...el.com> -- 1.7.1.1 -- best regards yang -- 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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