From c04fc586c1a480ba198f03ae7b6cbd7b57380b91 Mon Sep 17 00:00:00 2001 From: Gary Hade Date: Tue, 6 Jan 2009 14:39:14 -0800 Subject: mm: show node to memory section relationship with symlinks in sysfs 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 Signed-off-by: Badari Pulavarty Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/memory-hotplug.txt | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) (limited to 'Documentation/memory-hotplug.txt') diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt index 168117bd6ee..4c2ecf537a4 100644 --- a/Documentation/memory-hotplug.txt +++ b/Documentation/memory-hotplug.txt @@ -124,7 +124,7 @@ config options. This option can be kernel module too. -------------------------------- -3 sysfs files for memory hotplug +4 sysfs files for memory hotplug -------------------------------- All sections have their device information under /sys/devices/system/memory as @@ -138,11 +138,12 @@ For example, assume 1GiB section size. A device for a memory starting at (0x100000000 / 1Gib = 4) This device covers address range [0x100000000 ... 0x140000000) -Under each section, you can see 3 files. +Under each section, you can see 4 files. /sys/devices/system/memory/memoryXXX/phys_index /sys/devices/system/memory/memoryXXX/phys_device /sys/devices/system/memory/memoryXXX/state +/sys/devices/system/memory/memoryXXX/removable 'phys_index' : read-only and contains section id, same as XXX. 'state' : read-write @@ -150,10 +151,20 @@ Under each section, you can see 3 files. at write: user can specify "online", "offline" command 'phys_device': read-only: designed to show the name of physical memory device. This is not well implemented now. +'removable' : read-only: contains an integer value indicating + whether the memory section is removable or not + removable. A value of 1 indicates that the memory + section is removable and a value of 0 indicates that + it is not removable. NOTE: These directories/files appear after physical memory hotplug phase. +If CONFIG_NUMA is enabled the +/sys/devices/system/memory/memoryXXX memory section +directories can also be accessed via symbolic links located in +the /sys/devices/system/node/node* directories. For example: +/sys/devices/system/node/node0/memory9 -> ../../memory/memory9 -------------------------------- 4. Physical memory hot-add phase @@ -365,7 +376,6 @@ node if necessary. - allowing memory hot-add to ZONE_MOVABLE. maybe we need some switch like sysctl or new control file. - showing memory section and physical device relationship. - - showing memory section and node relationship (maybe good for NUMA) - showing memory section is under ZONE_MOVABLE or not - test and make it better memory offlining. - support HugeTLB page migration and offlining. -- cgit v1.2.3-70-g09d2