1DAXCTL-MIGRATE-DEV(1)                                    DAXCTL-MIGRATE-DEV(1)
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NAME

6       daxctl-migrate-device-model - Opt-in to the /sys/bus/dax device-model,
7       allow for alternative Device-DAX instance drivers.
8

SYNOPSIS

10       daxctl migrate-device-model
11
12       Arrange for modprobe to disable the dax_pmem_compat, if present, and
13       instead deploy the dax_pmem module to convert to the /sys/bus/dax
14       model. Kernel versions prior to v5.1 may not support /sys/bus/dax in
15       which case the result of this command is a nop until the kernel is
16       updated. The motivation for changing from /sys/class/dax to
17       /sys/bus/dax is to allow for alternative drivers for Device-DAX
18       instances, in particular the dax_kmem driver.
19
20       By default device-dax publishes a /dev/daxX.Y character device for
21       userspace to directly map performance differentiated memory. This is
22       fine if the memory is to be exclusively consumed / managed by
23       userspace. Alternatively an administrator may want the kernel to manage
24       the memory, make it available via malloc(), allow for
25       over-provisioning, and / or apply kernel-based resource control schemes
26       to the memory. In that case the memory fronted by a given Device-DAX
27       instance can be assigned to the dax_kmem driver which arranges for the
28       core-kernel memory-management sub-system to assume management of the
29       memory range.
30
31       This behavior is opt-in for consideration of existing applications /
32       scripts that may be hard coded to use /sys/class/dax. Fixes have been
33       submitted to applications known to have these direct dependencies
34       FIO[1] PMDK[2], however, there may be others and a system-owner should
35       be aware of the potential for regression of Device-DAX consuming
36       scripts, applications, or older daxctl binaries.
37
38       The modprobe policy established by this utility becomes effective after
39       the next reboot, or after all DAX related modules have been removed and
40       re-loaded with "udevadm trigger"
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43       Copyright © 2016 - 2022, Intel Corporation. License GPLv2: GNU GPL
44       version 2 http://gnu.org/licenses/gpl.html. This is free software: you
45       are free to change and redistribute it. There is NO WARRANTY, to the
46       extent permitted by law.
47

NOTES

49        1. FIO
50           http://git.kernel.dk/cgit/fio/commit/?id=b08e7d6b18b4
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52        2. PMDK
53           https://github.com/pmem/pmdk/commit/91bc8620884e
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57                                  01/13/2023             DAXCTL-MIGRATE-DEV(1)
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