Hi, On Thu, May 13, 2010 at 07:36:30PM +0800, Shaohui Zheng wrote: > Hi, All > This patchset introduces NUMA hotplug emulator for x86. it refers too > many files and might introduce new bugs, so we send a RFC to comminity first > and expect comments and suggestions, thanks. > <snip> > * Principles & Usages > > NUMA hotplug emulator include 3 different parts, We add a menu item to the > menuconfig to enable/disable them > (Refer to http://shaohui.org/images/hpe-krnl-cfg.jpg) > > > 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 > I tried the patchset on a non-NUMA machine. So, inorder to create fake NUMA nodes and be able to emulate the hotplug behavior, I used the following commandline: "numa=fake=4 numa=hide=2*2048" on a machine with 8G memory. I expected to see 4 nodes, out of which 2 would be hidden. However, the system comes up the 4 online nodes and 2 offline nodes (thus a total of 6 nodes). While we could decide this to be the semantics, however, I feel that numa=fake should define the total number of nodes. So in the above case, the system should have come up with 2 online nodes and 2 offline nodes. Also, "numa=hide=N" could also be supported, with the size of the hidden nodes being equal to the entire size of the node, with or without numa=fake parameter. On onlining one of the offline nodes, I see another issue that the memory under it is not automatically brought online. For example: #ls /sys/devices/system/node .... node0 node1 node2.. #cat /sys/devices/system/node/probe 3 #echo 3 > /sys/devices/system/node/probe #ls /sys/devices/system/node .... node0 node1 node2 node3 #cat /sys/devices/system/node/node3/meminfo Node 3 MemTotal: 0 kB Node 3 MemFree: 0 kB Node 3 MemUsed: 0 kB Node 3 Active: 0 kB ...... i.e, as memory-less nodes. However, these nodes were designated to have memory. So, on onlining the nodes, maybe we could have all their memory brought into online state as well ? -- Regards, Ankita Garg (ankita@xxxxxxxxxx) Linux Technology Center IBM India Systems & Technology Labs, Bangalore, India -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
