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Subject[8/8, v6] NUMA Hotplug Emulator: implement debugfs interface for memory probe
From: Shaohui Zheng <shaohui.zheng@intel.com>

Implement a debugfs inteface /sys/kernel/debug/mem_hotplug/probe for meomory hotplug
emulation. it accepts the same parameters like
/sys/devices/system/memory/probe.

Document the interface usage to file Documentation/memory-hotplug.txt.

CC: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Shaohui Zheng <shaohui.zheng@intel.com>
Signed-off-by: Haicheng Li <haicheng.li@intel.com>
--
Index: linux-hpe4/mm/memory_hotplug.c
===================================================================
--- linux-hpe4.orig/mm/memory_hotplug.c 2010-11-30 14:15:23.587622002 +0800
+++ linux-hpe4/mm/memory_hotplug.c 2010-11-30 14:16:45.447622001 +0800
@@ -983,4 +983,35 @@
}

module_init(node_debug_init);
+
+#ifdef CONFIG_ARCH_MEMORY_PROBE
+
+static ssize_t debug_memory_probe_store(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ return parse_memory_probe_store(buf, count);
+}
+
+static const struct file_operations memory_probe_file_ops = {
+ .write = debug_memory_probe_store,
+ .llseek = generic_file_llseek,
+};
+
+static int __init memory_debug_init(void)
+{
+ if (!memhp_debug_root)
+ memhp_debug_root = debugfs_create_dir("mem_hotplug", NULL);
+ if (!memhp_debug_root)
+ return -ENOMEM;
+
+ if (!debugfs_create_file("probe", S_IWUSR, memhp_debug_root,
+ NULL, &memory_probe_file_ops))
+ return -ENOMEM;
+
+ return 0;
+}
+
+module_init(memory_debug_init);
+
+#endif /* CONFIG_ARCH_MEMORY_PROBE */
#endif /* CONFIG_DEBUG_FS */
Index: linux-hpe4/Documentation/memory-hotplug.txt
===================================================================
--- linux-hpe4.orig/Documentation/memory-hotplug.txt 2010-11-30 14:15:23.587622002 +0800
+++ linux-hpe4/Documentation/memory-hotplug.txt 2010-11-30 14:40:27.267622000 +0800
@@ -198,23 +198,41 @@
In some environments, especially virtualized environment, firmware will not
notify memory hotplug event to the kernel. For such environment, "probe"
interface is supported. This interface depends on CONFIG_ARCH_MEMORY_PROBE.
+It can be also used for physical memory hotplug emulation.

-Now, CONFIG_ARCH_MEMORY_PROBE is supported only by powerpc but it does not
-contain highly architecture codes. Please add config if you need "probe"
+Now, CONFIG_ARCH_MEMORY_PROBE is supported by powerpc and x86_64, but it does
+not contain highly architecture codes. Please add config if you need "probe"
interface.

-Probe interface is located at
-/sys/devices/system/memory/probe
+We have both sysfs and debugfs interface for memory probe. They are located at
+/sys/devices/system/memory/probe (sysfs) and /sys/kernel/debug/mem_hotplug/probe
+(debugfs), We can try any of them, they accpet the same parameters.

You can tell the physical address of new memory to the kernel by

-% echo start_address_of_new_memory > /sys/devices/system/memory/probe
+% echo start_address_of_new_memory > memory/probe

Then, [start_address_of_new_memory, start_address_of_new_memory + section_size)
memory range is hot-added. In this case, hotplug script is not called (in
current implementation). You'll have to online memory by yourself.
Please see "How to online memory" in this text.

+The probe interface can accept flexible parameters, for example:
+
+Add a memory section(128M) to node 3(boots with mem=1024m)
+
+ echo 0x40000000,3 > memory/probe
+
+And more we make it friendly, it is possible to add memory to do
+
+ echo 3g > memory/probe
+ echo 1024m,3 > memory/probe
+
+Another format suggested by Dave Hansen:
+
+ echo physical_address=0x40000000 numa_node=3 > memory/probe
+
+You can also use mem_hotplug/probe(debugfs) interface in the above examples.

4.3 Node hotplug emulation
------------
--
Thanks & Regards,
Shaohui




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