diff options
author | Mike Rapoport <rppt@linux.vnet.ibm.com> | 2018-10-11 07:58:16 +0300 |
---|---|---|
committer | Jonathan Corbet <corbet@lwn.net> | 2018-10-12 11:13:57 -0600 |
commit | 52d7e21fd5677829353f7490723adf5f61999d84 (patch) | |
tree | afded23ad08b7c83deeb48e92d4f9e2b1f87ec79 /Documentation/core-api/memory-hotplug.rst | |
parent | 44ba0bb4f2ad96246cb1f20c041f4d062cf6c4c2 (diff) | |
download | linux-52d7e21fd5677829353f7490723adf5f61999d84.tar.gz linux-52d7e21fd5677829353f7490723adf5f61999d84.tar.bz2 linux-52d7e21fd5677829353f7490723adf5f61999d84.zip |
docs/core-api: rename memory-hotplug-notifier to memory-hotplug
to allow additions of new documentation about memory hotplug under the same
roof.
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/core-api/memory-hotplug.rst')
-rw-r--r-- | Documentation/core-api/memory-hotplug.rst | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/Documentation/core-api/memory-hotplug.rst b/Documentation/core-api/memory-hotplug.rst new file mode 100644 index 000000000000..a99f2f264725 --- /dev/null +++ b/Documentation/core-api/memory-hotplug.rst @@ -0,0 +1,87 @@ +.. _memory_hotplug: + +============== +Memory hotplug +============== + +Memory hotplug event notifier +============================= + +Hotplugging events are sent to a notification queue. + +There are six types of notification defined in ``include/linux/memory.h``: + +MEM_GOING_ONLINE + Generated before new memory becomes available in order to be able to + prepare subsystems to handle memory. The page allocator is still unable + to allocate from the new memory. + +MEM_CANCEL_ONLINE + Generated if MEM_GOING_ONLINE fails. + +MEM_ONLINE + Generated when memory has successfully brought online. The callback may + allocate pages from the new memory. + +MEM_GOING_OFFLINE + Generated to begin the process of offlining memory. Allocations are no + longer possible from the memory but some of the memory to be offlined + is still in use. The callback can be used to free memory known to a + subsystem from the indicated memory block. + +MEM_CANCEL_OFFLINE + Generated if MEM_GOING_OFFLINE fails. Memory is available again from + the memory block that we attempted to offline. + +MEM_OFFLINE + Generated after offlining memory is complete. + +A callback routine can be registered by calling:: + + hotplug_memory_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 memory_notify:: + + struct memory_notify { + unsigned long start_pfn; + unsigned long nr_pages; + int status_change_nid_normal; + int status_change_nid_high; + 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_high is set node id when N_HIGH_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. + +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 MEM_GOING_ONLINE, MEM_GOING_OFFLINE, +MEM_ONLINE, or MEM_OFFLINE action to cancel hotplugging. It stops +further processing of the notification queue. + +NOTIFY_STOP stops further processing of the notification queue. |