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1What: /sys/devices/system/memory2Date: June 20083Contact: Badari Pulavarty <pbadari@us.ibm.com>4Description:5 The /sys/devices/system/memory contains a snapshot of the6 internal state of the kernel memory blocks. Files could be7 added or removed dynamically to represent hot-add/remove8 operations.9Users: hotplug memory add/remove tools10 http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils11 12What: /sys/devices/system/memory/memoryX/removable13Date: June 200814Contact: Badari Pulavarty <pbadari@us.ibm.com>15Description:16 The file /sys/devices/system/memory/memoryX/removable is a17 legacy interface used to indicated whether a memory block is18 likely to be offlineable or not. Newer kernel versions return19 "1" if and only if the kernel supports memory offlining.20Users: hotplug memory remove tools21 http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils22 lsmem/chmem part of util-linux23 24What: /sys/devices/system/memory/memoryX/phys_device25Date: September 200826Contact: Badari Pulavarty <pbadari@us.ibm.com>27Description:28 The file /sys/devices/system/memory/memoryX/phys_device29 is read-only; it is a legacy interface only ever used on s390x30 to expose the covered storage increment.31Users: Legacy s390-tools lsmem/chmem32 33What: /sys/devices/system/memory/memoryX/phys_index34Date: September 200835Contact: Badari Pulavarty <pbadari@us.ibm.com>36Description:37 The file /sys/devices/system/memory/memoryX/phys_index38 is read-only and contains the section ID in hexadecimal39 which is equivalent to decimal X contained in the40 memory section directory name.41 42What: /sys/devices/system/memory/memoryX/state43Date: September 200844Contact: Badari Pulavarty <pbadari@us.ibm.com>45Description:46 The file /sys/devices/system/memory/memoryX/state47 is read-write. When read, it returns the online/offline48 state of the memory block. When written, root can toggle49 the online/offline state of a memory block using the following50 commands::51 52 # echo online > /sys/devices/system/memory/memoryX/state53 # echo offline > /sys/devices/system/memory/memoryX/state54 55 On newer kernel versions, advanced states can be specified56 when onlining to select a target zone: "online_movable"57 selects the movable zone. "online_kernel" selects the58 applicable kernel zone (DMA, DMA32, or Normal). However,59 after successfully setting one of the advanced states,60 reading the file will return "online"; the zone information61 can be obtained via "valid_zones" instead.62 63 While onlining is unlikely to fail, there are no guarantees64 that offlining will succeed. Offlining is more likely to65 succeed if "valid_zones" indicates "Movable".66Users: hotplug memory remove tools67 http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils68 69 70What: /sys/devices/system/memory/memoryX/valid_zones71Date: July 201472Contact: Zhang Zhen <zhenzhang.zhang@huawei.com>73Description:74 The file /sys/devices/system/memory/memoryX/valid_zones is75 read-only.76 77 For online memory blocks, it returns in which zone memory78 provided by a memory block is managed. If multiple zones79 apply (not applicable for hotplugged memory), "None" is returned80 and the memory block cannot be offlined.81 82 For offline memory blocks, it returns by which zone memory83 provided by a memory block can be managed when onlining.84 The first returned zone ("default") will be used when setting85 the state of an offline memory block to "online". Only one of86 the kernel zones (DMA, DMA32, Normal) is applicable for a single87 memory block.88 89What: /sys/devices/system/memoryX/nodeY90Date: October 200991Contact: Linux Memory Management list <linux-mm@kvack.org>92Description:93 When CONFIG_NUMA is enabled, a symbolic link that94 points to the corresponding NUMA node directory.95 96 For example, the following symbolic link is created for97 memory section 9 on node0:98 99 /sys/devices/system/memory/memory9/node0 -> ../../node/node0100 101 102What: /sys/devices/system/node/nodeX/memoryY103Date: September 2008104Contact: Gary Hade <garyhade@us.ibm.com>105Description:106 When CONFIG_NUMA is enabled107 /sys/devices/system/node/nodeX/memoryY is a symbolic link that108 points to the corresponding /sys/devices/system/memory/memoryY109 memory section directory. For example, the following symbolic110 link is created for memory section 9 on node0.111 112 /sys/devices/system/node/node0/memory9 -> ../../memory/memory9113 114What: /sys/devices/system/memory/crash_hotplug115Date: Aug 2023116Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>117Description:118 (RO) indicates whether or not the kernel updates relevant kexec119 segments on memory hot un/plug and/or on/offline events, avoiding the120 need to reload kdump kernel.121