•Reconfigure dax0.0 to system-ram mode, don’t online the memory

# daxctl reconfigure-device --mode=system-ram --no-online dax0.0
[
  {
    "chardev":"dax0.0",
    "size":16777216000,
    "target_node":2,
    "mode":"system-ram"
  }
]

•Reconfigure dax0.0 to devdax mode, attempt to offline the memory

# daxctl reconfigure-device --human --mode=devdax --force dax0.0
{
  "chardev":"dax0.0",
  "size":"15.63 GiB (16.78 GB)",
  "target_node":2,
  "mode":"devdax"
}

•Reconfigure all dax devices on region0 to system-ram mode

# daxctl reconfigure-device --mode=system-ram --region=0 all
[
  {
    "chardev":"dax0.0",
    "size":16777216000,
    "target_node":2,
    "mode":"system-ram"
  },
  {
    "chardev":"dax0.1",
    "size":16777216000,
    "target_node":3,
    "mode":"system-ram"
  }
]

•Run a process called some-service using numactl to restrict its cpu nodes to 0 and 1, and memory allocations to node 2 (determined using daxctl_dev_get_target_node() or daxctl list)

# daxctl reconfigure-device --mode=system-ram dax0.0
[
  {
    "chardev":"dax0.0",
    "size":16777216000,
    "target_node":2,
    "mode":"system-ram"
  }
]
# numactl --cpunodebind=0-1 --membind=2 -- some-service --opt1 --opt2

•Change the size of a dax device

# daxctl reconfigure-device dax0.1 -s 16G
reconfigured 1 device
# daxctl reconfigure-device dax0.1 -s 0
reconfigured 1 device

Note

This is a destructive operation. Any data on the dax device will be
lost.

Note

Device reconfiguration depends on the dax-bus device model. See
daxctl-migrate-device-model(1) for more information. If dax-class is in use (via the dax_pmem_compat driver), the reconfiguration will fail with an error such as the following:

# daxctl reconfigure-device --mode=system-ram --region=0 all
libdaxctl: daxctl_dev_disable: dax3.0: error: device model is dax-class
dax3.0: disable failed: Operation not supported
error reconfiguring devices: Operation not supported
reconfigured 0 devices

Restrict the operation to devices belonging to the specified region(s). A device-dax region is a contiguous range of memory that hosts one or more /dev/daxX.Y devices, where X is the region id and Y is the device instance id.

For regions that support dax device creation, change the device size in bytes. This option supports the suffixes "k" or "K" for KiB, "m" or "M" for MiB, "g" or "G" for GiB and "t" or "T" for TiB.

Applications that want to establish dax memory mappings with page table entries greater than system base page size (4K on x86) need a device that is sufficiently aligned. This defaults to 2M. Note that "devdax" mode enforces all mappings to be aligned to this value, i.e. it fails unaligned mapping attempts.

Specify the mode to which the dax device(s) should be reconfigured.

By default, memory sections provided by system-ram devices will be brought online automatically and immediately with the online_movable policy. Use this option to disable the automatic onlining behavior.

--movable is the default. This can be overridden to online new memory such that it is not movable. This allows any allocation to potentially be served from this memory. This may preclude subsequent removal. With the --movable behavior (which is default), kernel allocations will not consider this memory, and it will be reserved for application use.

When converting from "system-ram" mode to "devdax", it is expected that all the memory sections are first made offline. By default, daxctl won’t touch online memory. However with this option, attempt to offline the memory on the NUMA node associated with the dax device before converting it back to "devdax" mode.

By default the command will output machine-friendly raw-integer data. Instead, with this flag, numbers representing storage size will be formatted as human readable strings with units, other fields are converted to hexadecimal strings.

Emit more debug messages