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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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