memory_hotplug: introduce CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE (8604d9e5) · Commits · 戴 / test

This patchset continues the work I started with commit ("memory-hotplug: add automatic onlining policy for the newly added memory"). Initially I was going to stop there and bring the policy setting logic to userspace. I met two issues on this way: 1) It is possible to have memory hotplugged at boot (e.g. with QEMU). These blocks stay offlined if we turn the onlining policy on by userspace. 2) My attempt to bring this policy setting to systemd failed, systemd maintainers suggest to change the default in kernel or ... to use tmpfiles.d to alter the policy (which looks like a hack to me): https://github.com/systemd/systemd/pull/2938 Here I suggest to add a config option to set the default value for the policy and a kernel command line parameter to make the override. This patch (of 2): Introduce config option to set the default value for memory hotplug onlining policy (/sys/devices/system/memory/auto_online_blocks). The reason one would want to turn this option on are to have early onlining for hotpluggable memory available at boot and to not require any userspace actions to make memory hotplug work. [akpm@linux-foundation.org: tweak Kconfig text] Signed-off-by:

Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Dan Williams <dan.j.williams@intel.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: David Vrabel <david.vrabel@citrix.com> Cc: David Rientjes <rientjes@google.com> Cc: Igor Mammedov <imammedo@redhat.com> Cc: Lennart Poettering <lennart@poettering.net> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

Documentation/memory-hotplug.txt

+5 −4

Original line number	Diff line number	Diff line
		@@ -261,10 +261,11 @@ it according to the policy which can be read from "auto_online_blocks" file:

		% cat /sys/devices/system/memory/auto_online_blocks

		The default is "offline" which means the newly added memory is not in a
		ready-to-use state and you have to "online" the newly added memory blocks
		manually. Automatic onlining can be requested by writing "online" to
		"auto_online_blocks" file:
		The default depends on the CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
		option. If it is disabled the default is "offline" which means the newly added
		memory is not in a ready-to-use state and you have to "online" the newly added
		memory blocks manually. Automatic onlining can be requested by writing "online"
		to "auto_online_blocks" file:

		% echo online > /sys/devices/system/memory/auto_online_blocks

mm/Kconfig

+16 −0

Original line number	Diff line number	Diff line
		@@ -192,6 +192,22 @@ config MEMORY_HOTPLUG_SPARSE
		def_bool y
		depends on SPARSEMEM && MEMORY_HOTPLUG

		config MEMORY_HOTPLUG_DEFAULT_ONLINE
		bool "Online the newly added memory blocks by default"
		default n
		depends on MEMORY_HOTPLUG
		help
		This option sets the default policy setting for memory hotplug
		onlining policy (/sys/devices/system/memory/auto_online_blocks) which
		determines what happens to newly added memory regions. Policy setting
		can always be changed at runtime.
		See Documentation/memory-hotplug.txt for more information.

		Say Y here if you want all hot-plugged memory blocks to appear in
		'online' state by default.
		Say N here if you want the default policy to keep all hot-plugged
		memory blocks in 'offline' state.

		config MEMORY_HOTREMOVE
		bool "Allow for memory hot remove"
		select MEMORY_ISOLATION

mm/memory_hotplug.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -78,7 +78,11 @@ static struct {
		#define memhp_lock_acquire() lock_map_acquire(&mem_hotplug.dep_map)
		#define memhp_lock_release() lock_map_release(&mem_hotplug.dep_map)

		#ifndef CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE
		bool memhp_auto_online;
		#else
		bool memhp_auto_online = true;
		#endif
		EXPORT_SYMBOL_GPL(memhp_auto_online);

		void get_online_mems(void)

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