linux/Documentation/ABI/testing/sysfs-memory-page-offline

What:		/sys/devices/system/memory/soft_offline_page
Date:		Sep 2009
KernelVersion:	2.6.33
Contact:	andi@firstfloor.org
Description:
		Soft-offline the memory page containing the physical address
		written into this file. Input is a hex number specifying the
		physical address of the page. The kernel will then attempt
		to soft-offline it, by moving the contents elsewhere or
		dropping it if possible. The kernel will then be placed
		on the bad page list and never be reused.

		The offlining is done in kernel specific granuality.
		Normally it's the base page size of the kernel, but
		this might change.

		The page must be still accessible, not poisoned. The
		kernel will never kill anything for this, but rather
		fail the offline.  Return value is the size of the
		number, or a error when the offlining failed.  Reading
		the file is not allowed.

What:		/sys/devices/system/memory/hard_offline_page
Date:		Sep 2009
KernelVersion:	2.6.33
Contact:	andi@firstfloor.org
Description:
		Hard-offline the memory page containing the physical
		address written into this file. Input is a hex number
		specifying the physical address of the page. The
		kernel will then attempt to hard-offline the page, by
		trying to drop the page or killing any owner or
		triggering IO errors if needed.  Note this may kill
		any processes owning the page. The kernel will avoid
		to access this page assuming it's poisoned by the
		hardware.

		The offlining is done in kernel specific granuality.
		Normally it's the base page size of the kernel, but
		this might change.

		Return value is the size of the number, or a error when
		the offlining failed.
		Reading the file is not allowed.
HWPOISON: Add soft page offline support This is a simpler, gentler variant of memory_failure() for soft page offlining controlled from user space. It doesn't kill anything, just tries to invalidate and if that doesn't work migrate the page away. This is useful for predictive failure analysis, where a page has a high rate of corrected errors, but hasn't gone bad yet. Instead it can be offlined early and avoided. The offlining is controlled from sysfs, including a new generic entry point for hard page offlining for symmetry too. We use the page isolate facility to prevent re-allocation race. Normally this is only used by memory hotplug. To avoid races with memory allocation I am using lock_system_sleep(). This avoids the situation where memory hotplug is about to isolate a page range and then hwpoison undoes that work. This is a big hammer currently, but the simplest solution currently. When the page is not free or LRU we try to free pages from slab and other caches. The slab freeing is currently quite dumb and does not try to focus on the specific slab cache which might own the page. This could be potentially improved later. Thanks to Fengguang Wu and Haicheng Li for some fixes. [Added fix from Andrew Morton to adapt to new migrate_pages prototype] Signed-off-by: Andi Kleen <ak@linux.intel.com> 2009-12-16 11:20:00 +00:00			`What: /sys/devices/system/memory/soft_offline_page`
			`Date: Sep 2009`
			`KernelVersion: 2.6.33`
			`Contact: andi@firstfloor.org`
			`Description:`
			`Soft-offline the memory page containing the physical address`
			`written into this file. Input is a hex number specifying the`
			`physical address of the page. The kernel will then attempt`
			`to soft-offline it, by moving the contents elsewhere or`
			`dropping it if possible. The kernel will then be placed`
			`on the bad page list and never be reused.`

			`The offlining is done in kernel specific granuality.`
			`Normally it's the base page size of the kernel, but`
			`this might change.`

			`The page must be still accessible, not poisoned. The`
			`kernel will never kill anything for this, but rather`
			`fail the offline. Return value is the size of the`
			`number, or a error when the offlining failed. Reading`
			`the file is not allowed.`

			`What: /sys/devices/system/memory/hard_offline_page`
			`Date: Sep 2009`
			`KernelVersion: 2.6.33`
			`Contact: andi@firstfloor.org`
			`Description:`
			`Hard-offline the memory page containing the physical`
			`address written into this file. Input is a hex number`
			`specifying the physical address of the page. The`
			`kernel will then attempt to hard-offline the page, by`
			`trying to drop the page or killing any owner or`
			`triggering IO errors if needed. Note this may kill`
			`any processes owning the page. The kernel will avoid`
			`to access this page assuming it's poisoned by the`
			`hardware.`

			`The offlining is done in kernel specific granuality.`
			`Normally it's the base page size of the kernel, but`
			`this might change.`

			`Return value is the size of the number, or a error when`
			`the offlining failed.`
			`Reading the file is not allowed.`