From 98cee6742c80e35274bab06c5fa1141fe0abd910 Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Fri, 5 Oct 2018 01:11:01 +0300 Subject: 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 Signed-off-by: Jonathan Corbet --- Documentation/core-api/index.rst | 2 + Documentation/core-api/memory-hotplug-notifier.rst | 84 ++++++++++++++++++++++ 2 files changed, 86 insertions(+) create mode 100644 Documentation/core-api/memory-hotplug-notifier.rst (limited to 'Documentation/core-api') diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst index 165d76886d73..4f8a4266eb7c 100644 --- a/Documentation/core-api/index.rst +++ b/Documentation/core-api/index.rst @@ -32,6 +32,8 @@ Core utilities gfp_mask-from-fs-io timekeeping boot-time-mm + memory-hotplug-notifier + Interfaces for kernel debugging =============================== diff --git a/Documentation/core-api/memory-hotplug-notifier.rst b/Documentation/core-api/memory-hotplug-notifier.rst new file mode 100644 index 000000000000..35347cc3a43a --- /dev/null +++ b/Documentation/core-api/memory-hotplug-notifier.rst @@ -0,0 +1,84 @@ +.. _memory_hotplug_notifier: + +============================= +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. -- cgit