Shaohui, The documentation patch seems to be stale, it needs to be updated to match the new file names. On Tue, 07 Dec 2010, shaohui.zheng@xxxxxxxxx wrote: > 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. > > Reviewed-By: Randy Dunlap <randy.dunlap@xxxxxxxxxx> > Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx> > 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 2010-12-07 08:53:19.677622002 +0800 > @@ -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@0x80000000 > /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 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 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. 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 > mem_hotplug/node3/add_memory > + OR > + # echo 1024m > mem_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@xxxxxxxxxx> > +- Haicheng Li <haicheng.li@xxxxxxxxx> > +- Shaohui Zheng <shaohui.zheng@xxxxxxxxx> > + Nov 2010 > > -- > 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/ . > Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> >
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