bionic (5) systemd.resource-control.5.gz
NAME
systemd.resource-control - Resource control unit settings
SYNOPSIS
slice.slice, scope.scope, service.service, socket.socket, mount.mount, swap.swap
DESCRIPTION
Unit configuration files for services, slices, scopes, sockets, mount points, and swap devices share a
subset of configuration options for resource control of spawned processes. Internally, this relies on the
Linux Control Groups (cgroups) kernel concept for organizing processes in a hierarchical tree of named
groups for the purpose of resource management.
This man page lists the configuration options shared by those six unit types. See systemd.unit(5) for the
common options of all unit configuration files, and systemd.slice(5), systemd.scope(5),
systemd.service(5), systemd.socket(5), systemd.mount(5), and systemd.swap(5) for more information on the
specific unit configuration files. The resource control configuration options are configured in the
[Slice], [Scope], [Service], [Socket], [Mount], or [Swap] sections, depending on the unit type.
In addition, options which control resources available to programs executed by systemd are listed in
systemd.exec(5). Those options complement options listed here.
See the New Control Group Interfaces[1] for an introduction on how to make use of resource control APIs
from programs.
IMPLICIT DEPENDENCIES
The following dependencies are implicitly added:
• Units with the Slice= setting set automatically acquire Requires= and After= dependencies on the
specified slice unit.
UNIFIED AND LEGACY CONTROL GROUP HIERARCHIES
The unified control group hierarchy is the new version of kernel control group interface, see
cgroup-v2.txt[2]. Depending on the resource type, there are differences in resource control capabilities.
Also, because of interface changes, some resource types have separate set of options on the unified
hierarchy.
CPU
CPUWeight= and StartupCPUWeight= replace CPUShares= and StartupCPUShares=, respectively.
The "cpuacct" controller does not exist separately on the unified hierarchy.
Memory
MemoryMax= replaces MemoryLimit=. MemoryLow= and MemoryHigh= are effective only on unified
hierarchy.
IO
IO prefixed settings are a superset of and replace BlockIO prefixed ones. On unified hierarchy, IO
resource control also applies to buffered writes.
To ease the transition, there is best-effort translation between the two versions of settings. For each
controller, if any of the settings for the unified hierarchy are present, all settings for the legacy
hierarchy are ignored. If the resulting settings are for the other type of hierarchy, the configurations
are translated before application.
Legacy control group hierarchy (see cgroups.txt[3]), also called cgroup-v1, doesn't allow safe delegation
of controllers to unprivileged processes. If the system uses the legacy control group hierarchy, resource
control is disabled for systemd user instance, see systemd(1).
OPTIONS
Units of the types listed above can have settings for resource control configuration:
CPUAccounting=
Turn on CPU usage accounting for this unit. Takes a boolean argument. Note that turning on CPU
accounting for one unit will also implicitly turn it on for all units contained in the same slice and
for all its parent slices and the units contained therein. The system default for this setting may be
controlled with DefaultCPUAccounting= in systemd-system.conf(5).
CPUWeight=weight, StartupCPUWeight=weight
Assign the specified CPU time weight to the processes executed, if the unified control group
hierarchy is used on the system. These options take an integer value and control the "cpu.weight"
control group attribute. The allowed range is 1 to 10000. Defaults to 100. For details about this
control group attribute, see cgroup-v2.txt[2] and sched-design-CFS.txt[4]. The available CPU time is
split up among all units within one slice relative to their CPU time weight.
While StartupCPUWeight= only applies to the startup phase of the system, CPUWeight= applies to normal
runtime of the system, and if the former is not set also to the startup phase. Using
StartupCPUWeight= allows prioritizing specific services at boot-up differently than during normal
runtime.
Implies "CPUAccounting=true".
These settings replace CPUShares= and StartupCPUShares=.
CPUQuota=
Assign the specified CPU time quota to the processes executed. Takes a percentage value, suffixed
with "%". The percentage specifies how much CPU time the unit shall get at maximum, relative to the
total CPU time available on one CPU. Use values > 100% for allotting CPU time on more than one CPU.
This controls the "cpu.max" attribute on the unified control group hierarchy and "cpu.cfs_quota_us"
on legacy. For details about these control group attributes, see cgroup-v2.txt[2] and
sched-design-CFS.txt[4].
Example: CPUQuota=20% ensures that the executed processes will never get more than 20% CPU time on
one CPU.
Implies "CPUAccounting=true".
MemoryAccounting=
Turn on process and kernel memory accounting for this unit. Takes a boolean argument. Note that
turning on memory accounting for one unit will also implicitly turn it on for all units contained in
the same slice and for all its parent slices and the units contained therein. The system default for
this setting may be controlled with DefaultMemoryAccounting= in systemd-system.conf(5).
MemoryLow=bytes
Specify the best-effort memory usage protection of the executed processes in this unit. If the memory
usages of this unit and all its ancestors are below their low boundaries, this unit's memory won't be
reclaimed as long as memory can be reclaimed from unprotected units.
Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size
is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively.
Alternatively, a percentage value may be specified, which is taken relative to the installed physical
memory on the system. This controls the "memory.low" control group attribute. For details about this
control group attribute, see cgroup-v2.txt[2].
Implies "MemoryAccounting=true".
This setting is supported only if the unified control group hierarchy is used and disables
MemoryLimit=.
MemoryHigh=bytes
Specify the high limit on memory usage of the executed processes in this unit. Memory usage may go
above the limit if unavoidable, but the processes are heavily slowed down and memory is taken away
aggressively in such cases. This is the main mechanism to control memory usage of a unit.
Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size
is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively.
Alternatively, a percentage value may be specified, which is taken relative to the installed physical
memory on the system. If assigned the special value "infinity", no memory limit is applied. This
controls the "memory.high" control group attribute. For details about this control group attribute,
see cgroup-v2.txt[2].
Implies "MemoryAccounting=true".
This setting is supported only if the unified control group hierarchy is used and disables
MemoryLimit=.
MemoryMax=bytes
Specify the absolute limit on memory usage of the executed processes in this unit. If memory usage
cannot be contained under the limit, out-of-memory killer is invoked inside the unit. It is
recommended to use MemoryHigh= as the main control mechanism and use MemoryMax= as the last line of
defense.
Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size
is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively.
Alternatively, a percentage value may be specified, which is taken relative to the installed physical
memory on the system. If assigned the special value "infinity", no memory limit is applied. This
controls the "memory.max" control group attribute. For details about this control group attribute,
see cgroup-v2.txt[2].
Implies "MemoryAccounting=true".
This setting replaces MemoryLimit=.
MemorySwapMax=bytes
Specify the absolute limit on swap usage of the executed processes in this unit.
Takes a swap size in bytes. If the value is suffixed with K, M, G or T, the specified swap size is
parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. If
assigned the special value "infinity", no swap limit is applied. This controls the "memory.swap.max"
control group attribute. For details about this control group attribute, see cgroup-v2.txt[2].
Implies "MemoryAccounting=true".
This setting is supported only if the unified control group hierarchy is used and disables
MemoryLimit=.
TasksAccounting=
Turn on task accounting for this unit. Takes a boolean argument. If enabled, the system manager will
keep track of the number of tasks in the unit. The number of tasks accounted this way includes both
kernel threads and userspace processes, with each thread counting individually. Note that turning on
tasks accounting for one unit will also implicitly turn it on for all units contained in the same
slice and for all its parent slices and the units contained therein. The system default for this
setting may be controlled with DefaultTasksAccounting= in systemd-system.conf(5).
TasksMax=N
Specify the maximum number of tasks that may be created in the unit. This ensures that the number of
tasks accounted for the unit (see above) stays below a specific limit. This either takes an absolute
number of tasks or a percentage value that is taken relative to the configured maximum number of
tasks on the system. If assigned the special value "infinity", no tasks limit is applied. This
controls the "pids.max" control group attribute. For details about this control group attribute, see
pids.txt[5].
Implies "TasksAccounting=true". The system default for this setting may be controlled with
DefaultTasksMax= in systemd-system.conf(5).
IOAccounting=
Turn on Block I/O accounting for this unit, if the unified control group hierarchy is used on the
system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also
implicitly turn it on for all units contained in the same slice and all for its parent slices and the
units contained therein. The system default for this setting may be controlled with
DefaultIOAccounting= in systemd-system.conf(5).
This setting replaces BlockIOAccounting= and disables settings prefixed with BlockIO or
StartupBlockIO.
IOWeight=weight, StartupIOWeight=weight
Set the default overall block I/O weight for the executed processes, if the unified control group
hierarchy is used on the system. Takes a single weight value (between 1 and 10000) to set the default
block I/O weight. This controls the "io.weight" control group attribute, which defaults to 100. For
details about this control group attribute, see cgroup-v2.txt[2]. The available I/O bandwidth is
split up among all units within one slice relative to their block I/O weight.
While StartupIOWeight= only applies to the startup phase of the system, IOWeight= applies to the
later runtime of the system, and if the former is not set also to the startup phase. This allows
prioritizing specific services at boot-up differently than during runtime.
Implies "IOAccounting=true".
These settings replace BlockIOWeight= and StartupBlockIOWeight= and disable settings prefixed with
BlockIO or StartupBlockIO.
IODeviceWeight=device weight
Set the per-device overall block I/O weight for the executed processes, if the unified control group
hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to
specify the device specific weight value, between 1 and 10000. (Example: "/dev/sda 1000"). The file
path may be specified as path to a block device node or as any other file, in which case the backing
block device of the file system of the file is determined. This controls the "io.weight" control
group attribute, which defaults to 100. Use this option multiple times to set weights for multiple
devices. For details about this control group attribute, see cgroup-v2.txt[2].
Implies "IOAccounting=true".
This setting replaces BlockIODeviceWeight= and disables settings prefixed with BlockIO or
StartupBlockIO.
IOReadBandwidthMax=device bytes, IOWriteBandwidthMax=device bytes
Set the per-device overall block I/O bandwidth maximum limit for the executed processes, if the
unified control group hierarchy is used on the system. This limit is not work-conserving and the
executed processes are not allowed to use more even if the device has idle capacity. Takes a
space-separated pair of a file path and a bandwidth value (in bytes per second) to specify the device
specific bandwidth. The file path may be a path to a block device node, or as any other file in which
case the backing block device of the file system of the file is used. If the bandwidth is suffixed
with K, M, G, or T, the specified bandwidth is parsed as Kilobytes, Megabytes, Gigabytes, or
Terabytes, respectively, to the base of 1000. (Example:
"/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the "io.max" control group
attributes. Use this option multiple times to set bandwidth limits for multiple devices. For details
about this control group attribute, see cgroup-v2.txt[2].
Implies "IOAccounting=true".
These settings replace BlockIOReadBandwidth= and BlockIOWriteBandwidth= and disable settings prefixed
with BlockIO or StartupBlockIO.
IOReadIOPSMax=device IOPS, IOWriteIOPSMax=device IOPS
Set the per-device overall block I/O IOs-Per-Second maximum limit for the executed processes, if the
unified control group hierarchy is used on the system. This limit is not work-conserving and the
executed processes are not allowed to use more even if the device has idle capacity. Takes a
space-separated pair of a file path and an IOPS value to specify the device specific IOPS. The file
path may be a path to a block device node, or as any other file in which case the backing block
device of the file system of the file is used. If the IOPS is suffixed with K, M, G, or T, the
specified IOPS is parsed as KiloIOPS, MegaIOPS, GigaIOPS, or TeraIOPS, respectively, to the base of
1000. (Example: "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 1K"). This controls the "io.max"
control group attributes. Use this option multiple times to set IOPS limits for multiple devices. For
details about this control group attribute, see cgroup-v2.txt[2].
Implies "IOAccounting=true".
These settings are supported only if the unified control group hierarchy is used and disable settings
prefixed with BlockIO or StartupBlockIO.
IPAccounting=
Takes a boolean argument. If true, turns on IPv4 and IPv6 network traffic accounting for packets sent
or received by the unit. When this option is turned on, all IPv4 and IPv6 sockets created by any
process of the unit are accounted for. When this option is used in socket units, it applies to all
IPv4 and IPv6 sockets associated with it (including both listening and connection sockets where this
applies). Note that for socket-activated services, this configuration setting and the accounting data
of the service unit and the socket unit are kept separate, and displayed separately. No propagation
of the setting and the collected statistics is done, in either direction. Moreover, any traffic sent
or received on any of the socket unit's sockets is accounted to the socket unit — and never to the
service unit it might have activated, even if the socket is used by it. Note that IP accounting is
currently not supported for slice units, and enabling this option for them has no effect. The system
default for this setting may be controlled with DefaultIPAccounting= in systemd-system.conf(5).
IPAddressAllow=ADDRESS[/PREFIXLENGTH]..., IPAddressDeny=ADDRESS[/PREFIXLENGTH]...
Turn on address range network traffic filtering for packets sent and received over AF_INET and
AF_INET6 sockets. Both directives take a space separated list of IPv4 or IPv6 addresses, each
optionally suffixed with an address prefix length (separated by a "/" character). If the latter is
omitted, the address is considered a host address, i.e. the prefix covers the whole address (32 for
IPv4, 128 for IPv6).
The access lists configured with this option are applied to all sockets created by processes of this
unit (or in the case of socket units, associated with it). The lists are implicitly combined with any
lists configured for any of the parent slice units this unit might be a member of. By default all
access lists are empty. When configured the lists are enforced as follows:
• Access will be granted in case its destination/source address matches any entry in the
IPAddressAllow= setting.
• Otherwise, access will be denied in case its destination/source address matches any entry in the
IPAddressDeny= setting.
• Otherwise, access will be granted.
In order to implement a whitelisting IP firewall, it is recommended to use a IPAddressDeny=any
setting on an upper-level slice unit (such as the root slice -.slice or the slice containing all
system services system.slice – see systemd.special(7) for details on these slice units), plus
individual per-service IPAddressAllow= lines permitting network access to relevant services, and only
them.
Note that for socket-activated services, the IP access list configured on the socket unit applies to
all sockets associated with it directly, but not to any sockets created by the ultimately activated
services for it. Conversely, the IP access list configured for the service is not applied to any
sockets passed into the service via socket activation. Thus, it is usually a good idea, to replicate
the IP access lists on both the socket and the service unit, however it often makes sense to maintain
one list more open and the other one more restricted, depending on the usecase.
If these settings are used multiple times in the same unit the specified lists are combined. If an
empty string is assigned to these settings the specific access list is reset and all previous
settings undone.
In place of explicit IPv4 or IPv6 address and prefix length specifications a small set of symbolic
names may be used. The following names are defined:
Table 1. Special address/network names
┌──────────────┬──────────────────────────┬─────────────────────────────┐
│Symbolic Name │ Definition │ Meaning │
├──────────────┼──────────────────────────┼─────────────────────────────┤
│any │ 0.0.0.0/0 ::/0 │ Any host │
├──────────────┼──────────────────────────┼─────────────────────────────┤
│localhost │ 127.0.0.0/8 ::1/128 │ All addresses on the local │
│ │ │ loopback │
├──────────────┼──────────────────────────┼─────────────────────────────┤
│link-local │ 169.254.0.0/16 fe80::/64 │ All link-local IP addresses │
├──────────────┼──────────────────────────┼─────────────────────────────┤
│multicast │ 224.0.0.0/4 ff00::/8 │ All IP multicasting │
│ │ │ addresses │
└──────────────┴──────────────────────────┴─────────────────────────────┘
Note that these settings might not be supported on some systems (for example if eBPF control group
support is not enabled in the underlying kernel or container manager). These settings will have no
effect in that case. If compatibility with such systems is desired it is hence recommended to not
exclusively rely on them for IP security.
DeviceAllow=
Control access to specific device nodes by the executed processes. Takes two space-separated strings:
a device node specifier followed by a combination of r, w, m to control reading, writing, or creation
of the specific device node(s) by the unit (mknod), respectively. This controls the "devices.allow"
and "devices.deny" control group attributes. For details about these control group attributes, see
devices.txt[6].
The device node specifier is either a path to a device node in the file system, starting with /dev/,
or a string starting with either "char-" or "block-" followed by a device group name, as listed in
/proc/devices. The latter is useful to whitelist all current and future devices belonging to a
specific device group at once. The device group is matched according to filename globbing rules, you
may hence use the "*" and "?" wildcards. Examples: /dev/sda5 is a path to a device node, referring
to an ATA or SCSI block device. "char-pts" and "char-alsa" are specifiers for all pseudo TTYs and
all ALSA sound devices, respectively. "char-cpu/*" is a specifier matching all CPU related device
groups.
DevicePolicy=auto|closed|strict
Control the policy for allowing device access:
strict
means to only allow types of access that are explicitly specified.
closed
in addition, allows access to standard pseudo devices including /dev/null, /dev/zero, /dev/full,
/dev/random, and /dev/urandom.
auto
in addition, allows access to all devices if no explicit DeviceAllow= is present. This is the
default.
Slice=
The name of the slice unit to place the unit in. Defaults to system.slice for all non-instantiated
units of all unit types (except for slice units themselves see below). Instance units are by default
placed in a subslice of system.slice that is named after the template name.
This option may be used to arrange systemd units in a hierarchy of slices each of which might have
resource settings applied.
For units of type slice, the only accepted value for this setting is the parent slice. Since the name
of a slice unit implies the parent slice, it is hence redundant to ever set this parameter directly
for slice units.
Special care should be taken when relying on the default slice assignment in templated service units
that have DefaultDependencies=no set, see systemd.service(5), section "Default Dependencies" for
details.
Delegate=
Turns on delegation of further resource control partitioning to processes of the unit. Units where
this is enabled may create and manage their own private subhierarchy of control groups below the
control group of the unit itself. For unprivileged services (i.e. those using the User= setting) the
unit's control group will be made accessible to the relevant user. When enabled the service manager
will refrain from manipulating control groups or moving processes below the unit's control group, so
that a clear concept of ownership is established: the control group tree above the unit's control
group (i.e. towards the root control group) is owned and managed by the service manager of the host,
while the control group tree below the unit's control group is owned and managed by the unit itself.
Takes either a boolean argument or a list of control group controller names. If true, delegation is
turned on, and all supported controllers are enabled for the unit, making them available to the
unit's processes for management. If false, delegation is turned off entirely (and no additional
controllers are enabled). If set to a list of controllers, delegation is turned on, and the specified
controllers are enabled for the unit. Note that additional controllers than the ones specified might
be made available as well, depending on configuration of the containing slice unit or other units
contained in it. Note that assigning the empty string will enable delegation, but reset the list of
controllers, all assignments prior to this will have no effect. Defaults to false.
Note that controller delegation to less privileged code is only safe on the unified control group
hierarchy. Accordingly, access to the specified controllers will not be granted to unprivileged
services on the legacy hierarchy, even when requested.
The following controller names may be specified: cpu, cpuacct, io, blkio, memory, devices, pids. Not
all of these controllers are available on all kernels however, and some are specific to the unified
hierarchy while others are specific to the legacy hierarchy. Also note that the kernel might support
further controllers, which aren't covered here yet as delegation is either not supported at all for
them or not defined cleanly.
DEPRECATED OPTIONS
The following options are deprecated. Use the indicated superseding options instead:
CPUShares=weight, StartupCPUShares=weight
Assign the specified CPU time share weight to the processes executed. These options take an integer
value and control the "cpu.shares" control group attribute. The allowed range is 2 to 262144.
Defaults to 1024. For details about this control group attribute, see sched-design-CFS.txt[4]. The
available CPU time is split up among all units within one slice relative to their CPU time share
weight.
While StartupCPUShares= only applies to the startup phase of the system, CPUShares= applies to normal
runtime of the system, and if the former is not set also to the startup phase. Using
StartupCPUShares= allows prioritizing specific services at boot-up differently than during normal
runtime.
Implies "CPUAccounting=true".
These settings are deprecated. Use CPUWeight= and StartupCPUWeight= instead.
MemoryLimit=bytes
Specify the limit on maximum memory usage of the executed processes. The limit specifies how much
process and kernel memory can be used by tasks in this unit. Takes a memory size in bytes. If the
value is suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes,
Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be
specified, which is taken relative to the installed physical memory on the system. If assigned the
special value "infinity", no memory limit is applied. This controls the "memory.limit_in_bytes"
control group attribute. For details about this control group attribute, see memory.txt[7].
Implies "MemoryAccounting=true".
This setting is deprecated. Use MemoryMax= instead.
BlockIOAccounting=
Turn on Block I/O accounting for this unit, if the legacy control group hierarchy is used on the
system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also
implicitly turn it on for all units contained in the same slice and all for its parent slices and the
units contained therein. The system default for this setting may be controlled with
DefaultBlockIOAccounting= in systemd-system.conf(5).
This setting is deprecated. Use IOAccounting= instead.
BlockIOWeight=weight, StartupBlockIOWeight=weight
Set the default overall block I/O weight for the executed processes, if the legacy control group
hierarchy is used on the system. Takes a single weight value (between 10 and 1000) to set the default
block I/O weight. This controls the "blkio.weight" control group attribute, which defaults to 500.
For details about this control group attribute, see blkio-controller.txt[8]. The available I/O
bandwidth is split up among all units within one slice relative to their block I/O weight.
While StartupBlockIOWeight= only applies to the startup phase of the system, BlockIOWeight= applies
to the later runtime of the system, and if the former is not set also to the startup phase. This
allows prioritizing specific services at boot-up differently than during runtime.
Implies "BlockIOAccounting=true".
These settings are deprecated. Use IOWeight= and StartupIOWeight= instead.
BlockIODeviceWeight=device weight
Set the per-device overall block I/O weight for the executed processes, if the legacy control group
hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to
specify the device specific weight value, between 10 and 1000. (Example: "/dev/sda 500"). The file
path may be specified as path to a block device node or as any other file, in which case the backing
block device of the file system of the file is determined. This controls the "blkio.weight_device"
control group attribute, which defaults to 1000. Use this option multiple times to set weights for
multiple devices. For details about this control group attribute, see blkio-controller.txt[8].
Implies "BlockIOAccounting=true".
This setting is deprecated. Use IODeviceWeight= instead.
BlockIOReadBandwidth=device bytes, BlockIOWriteBandwidth=device bytes
Set the per-device overall block I/O bandwidth limit for the executed processes, if the legacy
control group hierarchy is used on the system. Takes a space-separated pair of a file path and a
bandwidth value (in bytes per second) to specify the device specific bandwidth. The file path may be
a path to a block device node, or as any other file in which case the backing block device of the
file system of the file is used. If the bandwidth is suffixed with K, M, G, or T, the specified
bandwidth is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes, respectively, to the base of
1000. (Example: "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the
"blkio.throttle.read_bps_device" and "blkio.throttle.write_bps_device" control group attributes. Use
this option multiple times to set bandwidth limits for multiple devices. For details about these
control group attributes, see blkio-controller.txt[8].
Implies "BlockIOAccounting=true".
These settings are deprecated. Use IOReadBandwidthMax= and IOWriteBandwidthMax= instead.
SEE ALSO
systemd(1), systemd.unit(5), systemd.service(5), systemd.slice(5), systemd.scope(5), systemd.socket(5), systemd.mount(5), systemd.swap(5), systemd.exec(5), systemd.directives(7), systemd.special(7), The documentation for control groups and specific controllers in the Linux kernel: cgroups.txt[3], cpuacct.txt[9], memory.txt[7], blkio-controller.txt[8].
NOTES
1. New Control Group Interfaces
https://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/
2. cgroup-v2.txt
https://www.kernel.org/doc/Documentation/cgroup-v2.txt
3. cgroups.txt
https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
4. sched-design-CFS.txt
https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt
5. pids.txt
https://www.kernel.org/doc/Documentation/cgroup-v1/pids.txt
6. devices.txt
https://www.kernel.org/doc/Documentation/cgroup-v1/devices.txt
7. memory.txt
https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt
8. blkio-controller.txt
https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt
9. cpuacct.txt
https://www.kernel.org/doc/Documentation/cgroup-v1/cpuacct.txt