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Message-ID: <20101201003610.GA9453@shaohui> Date: Wed, 1 Dec 2010 08:36:10 +0800 From: Shaohui Zheng <shaohui.zheng@...el.com> To: David Rientjes <rientjes@...gle.com> Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, haicheng.li@...ux.intel.com, lethal@...ux-sh.org, ak@...ux.intel.com, shaohui.zheng@...ux.intel.com, dave@...ux.vnet.ibm.com, gregkh@...e.de, Haicheng Li <haicheng.li@...el.com> Subject: Re: [1/8, v6] NUMA Hotplug Emulator: documentation On Tue, Nov 30, 2010 at 04:19:00PM -0800, David Rientjes wrote: > Signed-off-by: David Rientjes <rientjes@...gle.com> Resend this patch after adding David's sign-off. Subject: NUMA Hotplug Emulator: documentation From: Shaohui Zheng <shaohui.zheng@...el.com> 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> --- Index: linux-hpe4/Documentation/x86/x86_64/numa_hotplug_emulator.txt =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-hpe4/Documentation/x86/x86_64/numa_hotplug_emulator.txt 2010-11-30 09:48:52.257622002 +0800 @@ -0,0 +1,104 @@ +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/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/node/node1, in this example. ] + +2) CPU hotplug emulation: + +The emulator reserve CPUs throu 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 nid > cpu/probe + + - to hot-remove CPU + $ echo nid > cpu/release + +3) Memory hotplug emulation: + +The emulator reserves memory before OS boots, the reserved memory region is +removed from e820 table, and they can be hot-added via the probe interface. +this interface was extended to support adding memory to the specified node. It +maintains backwards compatibility. + +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 0x40000000,3 > memory/probe + OR + $ echo 1024m,3 > memory/probe + OR + $ echo "physical_address=0x40000000 numa_node=3" > memory/probe + +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> + Nov 2010 -- Thanks & Regards, Shaohui -- 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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