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mm: show node to memory section relationship with symlinks in sysfs

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Show node to memory section relationship with symlinks in sysfs

Add /sys/devices/system/node/nodeX/memoryY symlinks for all
the memory sections located on nodeX.  For example:
/sys/devices/system/node/node1/memory135 -> ../../memory/memory135
indicates that memory section 135 resides on node1.

Also revises documentation to cover this change as well as updating
Documentation/ABI/testing/sysfs-devices-memory to include descriptions
of memory hotremove files 'phys_device', 'phys_index', and 'state'
that were previously not described there.

In addition to it always being a good policy to provide users with
the maximum possible amount of physical location information for
resources that can be hot-added and/or hot-removed, the following
are some (but likely not all) of the user benefits provided by
this change.
Immediate:
  - Provides information needed to determine the specific node
    on which a defective DIMM is located.  This will reduce system
    downtime when the node or defective DIMM is swapped out.
  - Prevents unintended onlining of a memory section that was
    previously offlined due to a defective DIMM.  This could happen
    during node hot-add when the user or node hot-add assist script
    onlines _all_ offlined sections due to user or script inability
    to identify the specific memory sections located on the hot-added
    node.  The consequences of reintroducing the defective memory
    could be ugly.
  - Provides information needed to vary the amount and distribution
    of memory on specific nodes for testing or debugging purposes.
Future:
  - Will provide information needed to identify the memory
    sections that need to be offlined prior to physical removal
    of a specific node.

Symlink creation during boot was tested on 2-node x86_64, 2-node
ppc64, and 2-node ia64 systems.  Symlink creation during physical
memory hot-add tested on a 2-node x86_64 system.

Signed-off-by: Gary Hade <garyhade@us.ibm.com>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Gary Hade 2009-01-06 14:39:14 -08:00 • committed by Linus Torvalds
parent ee53a891f4
commit c04fc586c1
14 changed files with 210 additions and 26 deletions
Download patch file Download diff file Expand all files Collapse all files

13
include/linux/node.h
View file

@ -26,6 +26,7 @@ struct node {
struct sys_device sysdev;
};
struct memory_block;
extern struct node node_devices[];
extern int register_node(struct node *, int, struct node *);
@ -35,6 +36,9 @@ extern int register_one_node(int nid);
extern void unregister_one_node(int nid);
extern int register_cpu_under_node(unsigned int cpu, unsigned int nid);
extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid);
extern int register_mem_sect_under_node(struct memory_block *mem_blk,
int nid);
extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk);
#else
static inline int register_one_node(int nid)
{
@ -52,6 +56,15 @@ static inline int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
{
return 0;
}
static inline int register_mem_sect_under_node(struct memory_block *mem_blk,
int nid)
{
return 0;
}
static inline int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
{
return 0;
}
#endif
#define to_node(sys_device) container_of(sys_device, struct node, sysdev)