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memory-hotplug: add sysfs removable attribute for hotplug memory remove
Memory may be hot-removed on a per-memory-block basis, particularly on POWER where the SPARSEMEM section size often matches the memory-block size. A user-level agent must be able to identify which sections of memory are likely to be removable before attempting the potentially expensive operation. This patch adds a file called "removable" to the memory directory in sysfs to help such an agent. In this patch, a memory block is considered removable if; o It contains only MOVABLE pageblocks o It contains only pageblocks with free pages regardless of pageblock type On the other hand, a memory block starting with a PageReserved() page will never be considered removable. Without this patch, the user-agent is forced to choose a memory block to remove randomly. Sample output of the sysfs files: ./memory/memory0/removable: 0 ./memory/memory1/removable: 0 ./memory/memory2/removable: 0 ./memory/memory3/removable: 0 ./memory/memory4/removable: 0 ./memory/memory5/removable: 0 ./memory/memory6/removable: 0 ./memory/memory7/removable: 1 ./memory/memory8/removable: 0 ./memory/memory9/removable: 0 ./memory/memory10/removable: 0 ./memory/memory11/removable: 0 ./memory/memory12/removable: 0 ./memory/memory13/removable: 0 ./memory/memory14/removable: 0 ./memory/memory15/removable: 0 ./memory/memory16/removable: 0 ./memory/memory17/removable: 1 ./memory/memory18/removable: 1 ./memory/memory19/removable: 1 ./memory/memory20/removable: 1 ./memory/memory21/removable: 1 ./memory/memory22/removable: 1 Signed-off-by: Badari Pulavarty <[email protected]> Signed-off-by: Mel Gorman <[email protected]> Acked-by: KAMEZAWA Hiroyuki <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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What: /sys/devices/system/memory | ||
Date: June 2008 | ||
Contact: Badari Pulavarty <[email protected]> | ||
Description: | ||
The /sys/devices/system/memory contains a snapshot of the | ||
internal state of the kernel memory blocks. Files could be | ||
added or removed dynamically to represent hot-add/remove | ||
operations. | ||
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Users: hotplug memory add/remove tools | ||
https://w3.opensource.ibm.com/projects/powerpc-utils/ | ||
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What: /sys/devices/system/memory/memoryX/removable | ||
Date: June 2008 | ||
Contact: Badari Pulavarty <[email protected]> | ||
Description: | ||
The file /sys/devices/system/memory/memoryX/removable | ||
indicates whether this memory block is removable or not. | ||
This is useful for a user-level agent to determine | ||
identify removable sections of the memory before attempting | ||
potentially expensive hot-remove memory operation | ||
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Users: hotplug memory remove tools | ||
https://w3.opensource.ibm.com/projects/powerpc-utils/ |
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