docs/vm: split memory hotplug notifier description to Documentation/core-api
The memory hotplug notifier description is about kernel internals rather than admin/user visible API. Place it appropriately. Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Mike Rapoport
Jonathan Corbet
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6bf53999a3
commit
98cee6742c
@ -31,7 +31,6 @@ be changed often.
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6.1 Memory offline and ZONE_MOVABLE
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6.2. How to offline memory
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7. Physical memory remove
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8. Memory hotplug event notifier
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9. Future Work List
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@ -414,88 +413,6 @@ Need more implementation yet....
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- Notification completion of remove works by OS to firmware.
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- Guard from remove if not yet.
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Memory hotplug event notifier
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=============================
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Hotplugging events are sent to a notification queue.
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There are six types of notification defined in ``include/linux/memory.h``:
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MEM_GOING_ONLINE
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Generated before new memory becomes available in order to be able to
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prepare subsystems to handle memory. The page allocator is still unable
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to allocate from the new memory.
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MEM_CANCEL_ONLINE
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Generated if MEMORY_GOING_ONLINE fails.
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MEM_ONLINE
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Generated when memory has successfully brought online. The callback may
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allocate pages from the new memory.
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MEM_GOING_OFFLINE
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Generated to begin the process of offlining memory. Allocations are no
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longer possible from the memory but some of the memory to be offlined
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is still in use. The callback can be used to free memory known to a
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subsystem from the indicated memory block.
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MEM_CANCEL_OFFLINE
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Generated if MEMORY_GOING_OFFLINE fails. Memory is available again from
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the memory block that we attempted to offline.
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MEM_OFFLINE
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Generated after offlining memory is complete.
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A callback routine can be registered by calling::
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hotplug_memory_notifier(callback_func, priority)
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Callback functions with higher values of priority are called before callback
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functions with lower values.
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A callback function must have the following prototype::
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int callback_func(
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struct notifier_block *self, unsigned long action, void *arg);
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The first argument of the callback function (self) is a pointer to the block
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of the notifier chain that points to the callback function itself.
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The second argument (action) is one of the event types described above.
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The third argument (arg) passes a pointer of struct memory_notify::
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struct memory_notify {
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unsigned long start_pfn;
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unsigned long nr_pages;
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int status_change_nid_normal;
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int status_change_nid_high;
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int status_change_nid;
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}
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- start_pfn is start_pfn of online/offline memory.
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- nr_pages is # of pages of online/offline memory.
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- status_change_nid_normal is set node id when N_NORMAL_MEMORY of nodemask
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is (will be) set/clear, if this is -1, then nodemask status is not changed.
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- status_change_nid_high is set node id when N_HIGH_MEMORY of nodemask
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is (will be) set/clear, if this is -1, then nodemask status is not changed.
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- status_change_nid is set node id when N_MEMORY of nodemask is (will be)
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set/clear. It means a new(memoryless) node gets new memory by online and a
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node loses all memory. If this is -1, then nodemask status is not changed.
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If status_changed_nid* >= 0, callback should create/discard structures for the
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node if necessary.
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The callback routine shall return one of the values
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NOTIFY_DONE, NOTIFY_OK, NOTIFY_BAD, NOTIFY_STOP
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defined in ``include/linux/notifier.h``
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NOTIFY_DONE and NOTIFY_OK have no effect on the further processing.
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NOTIFY_BAD is used as response to the MEM_GOING_ONLINE, MEM_GOING_OFFLINE,
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MEM_ONLINE, or MEM_OFFLINE action to cancel hotplugging. It stops
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further processing of the notification queue.
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NOTIFY_STOP stops further processing of the notification queue.
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Future Work
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===========
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@ -32,6 +32,8 @@ Core utilities
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gfp_mask-from-fs-io
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timekeeping
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boot-time-mm
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memory-hotplug-notifier
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Interfaces for kernel debugging
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===============================
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84
Documentation/core-api/memory-hotplug-notifier.rst
Normal file
84
Documentation/core-api/memory-hotplug-notifier.rst
Normal file
@ -0,0 +1,84 @@
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.. _memory_hotplug_notifier:
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=============================
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Memory hotplug event notifier
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=============================
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Hotplugging events are sent to a notification queue.
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There are six types of notification defined in ``include/linux/memory.h``:
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MEM_GOING_ONLINE
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Generated before new memory becomes available in order to be able to
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prepare subsystems to handle memory. The page allocator is still unable
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to allocate from the new memory.
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MEM_CANCEL_ONLINE
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Generated if MEM_GOING_ONLINE fails.
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MEM_ONLINE
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Generated when memory has successfully brought online. The callback may
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allocate pages from the new memory.
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MEM_GOING_OFFLINE
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Generated to begin the process of offlining memory. Allocations are no
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longer possible from the memory but some of the memory to be offlined
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is still in use. The callback can be used to free memory known to a
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subsystem from the indicated memory block.
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MEM_CANCEL_OFFLINE
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Generated if MEM_GOING_OFFLINE fails. Memory is available again from
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the memory block that we attempted to offline.
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MEM_OFFLINE
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Generated after offlining memory is complete.
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A callback routine can be registered by calling::
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hotplug_memory_notifier(callback_func, priority)
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Callback functions with higher values of priority are called before callback
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functions with lower values.
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A callback function must have the following prototype::
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int callback_func(
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struct notifier_block *self, unsigned long action, void *arg);
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The first argument of the callback function (self) is a pointer to the block
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of the notifier chain that points to the callback function itself.
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The second argument (action) is one of the event types described above.
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The third argument (arg) passes a pointer of struct memory_notify::
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struct memory_notify {
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unsigned long start_pfn;
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unsigned long nr_pages;
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int status_change_nid_normal;
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int status_change_nid_high;
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int status_change_nid;
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}
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- start_pfn is start_pfn of online/offline memory.
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- nr_pages is # of pages of online/offline memory.
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- status_change_nid_normal is set node id when N_NORMAL_MEMORY of nodemask
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is (will be) set/clear, if this is -1, then nodemask status is not changed.
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- status_change_nid_high is set node id when N_HIGH_MEMORY of nodemask
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is (will be) set/clear, if this is -1, then nodemask status is not changed.
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- status_change_nid is set node id when N_MEMORY of nodemask is (will be)
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set/clear. It means a new(memoryless) node gets new memory by online and a
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node loses all memory. If this is -1, then nodemask status is not changed.
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If status_changed_nid* >= 0, callback should create/discard structures for the
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node if necessary.
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The callback routine shall return one of the values
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NOTIFY_DONE, NOTIFY_OK, NOTIFY_BAD, NOTIFY_STOP
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defined in ``include/linux/notifier.h``
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NOTIFY_DONE and NOTIFY_OK have no effect on the further processing.
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NOTIFY_BAD is used as response to the MEM_GOING_ONLINE, MEM_GOING_OFFLINE,
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MEM_ONLINE, or MEM_OFFLINE action to cancel hotplugging. It stops
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further processing of the notification queue.
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NOTIFY_STOP stops further processing of the notification queue.
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