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Diffstat (limited to 'Documentation/core-api/memory-hotplug.rst')
| -rw-r--r-- | Documentation/core-api/memory-hotplug.rst | 91 |
1 files changed, 82 insertions, 9 deletions
diff --git a/Documentation/core-api/memory-hotplug.rst b/Documentation/core-api/memory-hotplug.rst index 682259ee633a..8fc97c2379de 100644 --- a/Documentation/core-api/memory-hotplug.rst +++ b/Documentation/core-api/memory-hotplug.rst @@ -9,6 +9,9 @@ Memory hotplug event notifier Hotplugging events are sent to a notification queue. +Memory notifier +---------------- + There are six types of notification defined in ``include/linux/memory.h``: MEM_GOING_ONLINE @@ -56,20 +59,18 @@ The third argument (arg) passes a pointer of struct memory_notify:: struct memory_notify { unsigned long start_pfn; unsigned long nr_pages; - int status_change_nid_normal; - int status_change_nid; } - start_pfn is start_pfn of online/offline memory. - nr_pages is # of pages of online/offline memory. -- status_change_nid_normal is set node id when N_NORMAL_MEMORY of nodemask - is (will be) set/clear, if this is -1, then nodemask status is not changed. -- status_change_nid is set node id when N_MEMORY of nodemask is (will be) - set/clear. It means a new(memoryless) node gets new memory by online and a - node loses all memory. If this is -1, then nodemask status is not changed. - If status_changed_nid* >= 0, callback should create/discard structures for the - node if necessary. +It is possible to get notified for MEM_CANCEL_ONLINE without having been notified +for MEM_GOING_ONLINE, and the same applies to MEM_CANCEL_OFFLINE and +MEM_GOING_OFFLINE. +This can happen when a consumer fails, meaning we break the callchain and we +stop calling the remaining consumers of the notifier. +It is then important that users of memory_notify make no assumptions and get +prepared to handle such cases. The callback routine shall return one of the values NOTIFY_DONE, NOTIFY_OK, NOTIFY_BAD, NOTIFY_STOP @@ -83,6 +84,78 @@ further processing of the notification queue. NOTIFY_STOP stops further processing of the notification queue. +Numa node notifier +------------------ + +There are six types of notification defined in ``include/linux/node.h``: + +NODE_ADDING_FIRST_MEMORY + Generated before memory becomes available to this node for the first time. + +NODE_CANCEL_ADDING_FIRST_MEMORY + Generated if NODE_ADDING_FIRST_MEMORY fails. + +NODE_ADDED_FIRST_MEMORY + Generated when memory has become available fo this node for the first time. + +NODE_REMOVING_LAST_MEMORY + Generated when the last memory available to this node is about to be offlined. + +NODE_CANCEL_REMOVING_LAST_MEMORY + Generated when NODE_CANCEL_REMOVING_LAST_MEMORY fails. + +NODE_REMOVED_LAST_MEMORY + Generated when the last memory available to this node has been offlined. + +A callback routine can be registered by calling:: + + hotplug_node_notifier(callback_func, priority) + +Callback functions with higher values of priority are called before callback +functions with lower values. + +A callback function must have the following prototype:: + + int callback_func( + + struct notifier_block *self, unsigned long action, void *arg); + +The first argument of the callback function (self) is a pointer to the block +of the notifier chain that points to the callback function itself. +The second argument (action) is one of the event types described above. +The third argument (arg) passes a pointer of struct node_notify:: + + struct node_notify { + int nid; + } + +- nid is the node we are adding or removing memory to. + +It is possible to get notified for NODE_CANCEL_ADDING_FIRST_MEMORY without +having been notified for NODE_ADDING_FIRST_MEMORY, and the same applies to +NODE_CANCEL_REMOVING_LAST_MEMORY and NODE_REMOVING_LAST_MEMORY. +This can happen when a consumer fails, meaning we break the callchain and we +stop calling the remaining consumers of the notifier. +It is then important that users of node_notify make no assumptions and get +prepared to handle such cases. + +The callback routine shall return one of the values +NOTIFY_DONE, NOTIFY_OK, NOTIFY_BAD, NOTIFY_STOP +defined in ``include/linux/notifier.h`` + +NOTIFY_DONE and NOTIFY_OK have no effect on the further processing. + +NOTIFY_BAD is used as response to the NODE_ADDING_FIRST_MEMORY, +NODE_REMOVING_LAST_MEMORY, NODE_ADDED_FIRST_MEMORY or +NODE_REMOVED_LAST_MEMORY action to cancel hotplugging. +It stops further processing of the notification queue. + +NOTIFY_STOP stops further processing of the notification queue. + +Please note that we should not fail for NODE_ADDED_FIRST_MEMORY / +NODE_REMOVED_FIRST_MEMORY, as memory_hotplug code cannot rollback at that +point anymore. + Locking Internals ================= |