From: Shaohui Zheng <shaohui.zheng@xxxxxxxxx> add a text file Documentation/x86/x86_64/numa_hotplug_emulator.txt to explain the usage for the hotplug emulator. Signed-off-by: Haicheng Li <haicheng.li@xxxxxxxxx> Signed-off-by: Shaohui Zheng <shaohui.zheng@xxxxxxxxx> --- 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 2010-11-17 09:01:10.342836513 +0800 @@ -0,0 +1,92 @@ +NUMA Hotplug Emulator for x86 +--------------------------------------------------- + +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: + +The emulator firstly hides RAM via E820 table, and then it can +fake offlined nodes with the hidden RAM. + +After system bootup, user is able to hotplug-add these offlined +nodes, which is just similar to a real hotplug hardware behavior. + +Using boot option "numa=hide=N*size" to fake offlined nodes: + - N is the number of hidden nodes + - size is the memory size (in MB) per hidden node. + +There is a sysfs entry "probe" under /sys/devices/system/node/ for user +to hotplug the fake offlined nodes: + + - to show all fake offlined nodes: + $ cat /sys/devices/system/node/probe + + - to hotadd a fake offlined node, e.g. nodeid is N: + $ echo N > /sys/devices/system/node/probe + +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 hotplug 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 an 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 initialize CPUs + - 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 reserve memory before OS booting, the reserved memory region +is remove from e820 table, and they can be hot-added via the probe interface, +this interface was extend to support add 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 throu grub parameter + 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 + +- Haicheng Li <haicheng.li@xxxxxxxxx> +- Shaohui Zheng <shaohui.zheng@xxxxxxxxx> + Nov 2010 Index: linux-hpe4/Documentation/x86/x86_64/boot-options.txt =================================================================== --- linux-hpe4.orig/Documentation/x86/x86_64/boot-options.txt 2010-11-17 10:01:37.093461435 +0800 +++ linux-hpe4/Documentation/x86/x86_64/boot-options.txt 2010-11-17 10:03:10.881043878 +0800 @@ -173,6 +173,13 @@ numa=fake=<N> If given as an integer, fills all system RAM with N fake nodes interleaved over physical nodes. + numa=hide=N*size1[,size2,...] + Give an string seperated by comma, each sub string stands for a serie nodes. + system will reserve an area to create hide numa nodes for them. + + for example: numa=hide=2*512,256 + system will reserve (2*512 + 256) M for 3 hide nodes. 2 nodes with 512M memory, + and 1 node with 256 memory ACPI @@ -316,3 +323,8 @@ Do not use GB pages for kernel direct mappings. gbpages Use GB pages for kernel direct mappings. + cpu_hpe=on/off + Enable/disable cpu hotplug emulation with software method. when cpu_hpe=on, + sysfs provides probe/release interface to hot add/remove cpu dynamically. + this option is disabled in default. + -- Thanks & Regards, Shaohui -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . 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