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Subject[7/7,v8] NUMA Hotplug Emulator: Implement per-node add_memory debugfs interface
From:  Shaohui Zheng <shaohui.zheng@intel.com>

Add add_memory interface to support to memory hotplug emulation for each online
node under debugfs. The reserved memory can be added into desired node with
this interface.

The layout on debugfs:
mem_hotplug/node0/add_memory
mem_hotplug/node1/add_memory
mem_hotplug/node2/add_memory
...

Add a memory section(128M) to node 3(boots with mem=1024m)

echo 0x40000000 > mem_hotplug/node3/add_memory
And more we make it friendly, it is possible to add memory to do

echo 1024m > mem_hotplug/node3/add_memory
CC: David Rientjes <rientjes@google.com>
CC: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Haicheng Li <haicheng.li@intel.com>
Signed-off-by: Shaohui Zheng <shaohui.zheng@intel.com>
---
Index: linux-hpe4/mm/memory_hotplug.c
===================================================================
--- linux-hpe4.orig/mm/memory_hotplug.c 2010-12-02 12:35:31.557622002 +0800
+++ linux-hpe4/mm/memory_hotplug.c 2010-12-06 07:30:36.067622001 +0800
@@ -930,6 +930,80 @@

static struct dentry *memhp_debug_root;

+#ifdef CONFIG_ARCH_MEMORY_PROBE
+
+static ssize_t add_memory_store(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ u64 phys_addr = 0;
+ int nid = file->private_data - NULL;
+ int ret;
+
+ phys_addr = simple_strtoull(buf, NULL, 0);
+ printk(KERN_INFO "Add a memory section to node: %d.\n", nid);
+ phys_addr = memparse(buf, NULL);
+ ret = add_memory(nid, phys_addr, PAGES_PER_SECTION << PAGE_SHIFT);
+
+ if (ret)
+ count = ret;
+
+ return count;
+}
+
+static int add_memory_open(struct inode *inode, struct file *file)
+{
+ file->private_data = inode->i_private;
+ return 0;
+}
+
+static const struct file_operations add_memory_file_ops = {
+ .open = add_memory_open,
+ .write = add_memory_store,
+ .llseek = generic_file_llseek,
+};
+
+/*
+ * Create add_memory debugfs entry under specified node
+ */
+static int debugfs_create_add_memory_entry(int nid)
+{
+ char buf[32];
+ static struct dentry *node_debug_root;
+
+ snprintf(buf, sizeof(buf), "node%d", nid);
+ node_debug_root = debugfs_create_dir(buf, memhp_debug_root);
+
+ /* the nid information was represented by the offset of pointer(NULL+nid) */
+ if (!debugfs_create_file("add_memory", S_IWUSR, node_debug_root,
+ NULL + nid, &add_memory_file_ops))
+ return -ENOMEM;
+
+ return 0;
+}
+
+static int __init memory_debug_init(void)
+{
+ int nid;
+
+ if (!memhp_debug_root)
+ memhp_debug_root = debugfs_create_dir("mem_hotplug", NULL);
+ if (!memhp_debug_root)
+ return -ENOMEM;
+
+ for_each_online_node(nid)
+ debugfs_create_add_memory_entry(nid);
+
+ return 0;
+}
+
+module_init(memory_debug_init);
+#else
+static debugfs_create_add_memory_entry(int nid)
+{
+ return 0;
+}
+#endif /* CONFIG_ARCH_MEMORY_PROBE */
+
static ssize_t add_node_store(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
@@ -960,6 +1034,8 @@
return -ENOMEM;

ret = add_memory(nid, start, size);
+
+ debugfs_create_add_memory_entry(nid);
return ret ? ret : count;
}

Index: linux-hpe4/Documentation/memory-hotplug.txt
===================================================================
--- linux-hpe4.orig/Documentation/memory-hotplug.txt 2010-12-02 12:35:31.557622002 +0800
+++ linux-hpe4/Documentation/memory-hotplug.txt 2010-12-06 07:39:36.007622000 +0800
@@ -19,6 +19,7 @@
4.1 Hardware(Firmware) Support
4.2 Notify memory hot-add event by hand
4.3 Node hotplug emulation
+ 4.4 Memory hotplug emulation
5. Logical Memory hot-add phase
5.1. State of memory
5.2. How to online memory
@@ -239,6 +240,29 @@
Once the new node has been added, it is possible to online the memory by
toggling the "state" of its memory section(s) as described in section 5.1.

+4.4 Memory hotplug emulation
+------------
+With debugfs, it is possible to test memory hotplug with software method, we
+can add memory section to desired node with add_memory interface. It is a much
+more powerful interface than "probe" described in section 4.2.
+
+There is an add_memory interface for each online node at the debugfs mount
+point.
+ mem_hotplug/node0/add_memory
+ mem_hotplug/node1/add_memory
+ mem_hotplug/node2/add_memory
+ ...
+
+Add a memory section(128M) to node 3(boots with mem=1024m)
+
+ echo 0x40000000 > mem_hotplug/node3/add_memory
+
+And more we make it friendly, it is possible to add memory to do
+
+ echo 1024m > mem_hotplug/node3/add_memory
+
+Once the new memory section has been added, it is possible to online the memory
+by toggling the "state" described in section 5.1.

------------------------------
5. Logical Memory hot-add phase
--
Thanks & Regards,
Shaohui




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