.TH "cgroup.conf" "5" "Slurm Configuration File" "July 2024" "Slurm Configuration File"

.SH "NAME"
cgroup.conf \- Slurm configuration file for the cgroup support

.SH "DESCRIPTION"

\fBcgroup.conf\fP is an ASCII file which defines parameters used by
Slurm's Linux cgroup related plugins.
The file will always be located in the same directory as the \fBslurm.conf\fR.
.LP
Parameter names are case insensitive.
Any text following a "#" in the configuration file is treated
as a comment through the end of that line.
Changes to the configuration file take effect upon restart of
Slurm daemons, daemon receipt of the SIGHUP signal, or execution
of the command "scontrol reconfigure" unless otherwise noted.

.LP
For general Slurm cgroups information, see the Cgroups Guide at
<https://slurm.schedmd.com/cgroups.html>.

.LP
The following cgroup.conf parameters are defined to control the general behavior
of Slurm cgroup plugins.

.TP
\fBCgroupMountpoint\fR=\fIPATH\fR
Only intended for development and testing. Specifies the \fIPATH\fR under which
cgroup controllers should be mounted. The default \fIPATH\fR is /sys/fs/cgroup.
.IP

.TP
\fBCgroupPlugin\fR=\fI<cgroup/v1|cgroup/v2|autodetect|disabled>\fR
Specify the plugin to be used when interacting with the cgroup subsystem.
Supported values are "disabled", to completely disable any interaction with
the cgroups, "cgroup/v1" which supports the legacy interface of cgroup v1,
"cgroup/v2" for the unified cgroup2 architecture, and "autodetect" which tries
to determine which cgroup version does your system provide. "autodetect" is
useful to have a single configuration in clusters where nodes can have different
cgroup versions. The default value is "autodetect".
.IP

.TP
\fBSystemdTimeout\fR=\fI<number>\fR
On slow systems like virtual machines or when systemd is busy, it can take
a lot of time to initialize and prepare the scope for slurmd during startup.
Slurm will wait a maximum of this amount of time (in milliseconds) for the
scope to be ready before failing. Only applies to cgroup/v2.
The default is 1000 ms.
.IP

.TP
\fBIgnoreSystemd\fR=\fI<yes|no>\fR
Only for cgroup/v2 and for development and testing. It will avoid any call to
dbus and contact with systemd, and instead will prepare all the cgroup hierarchy
manually. This option is dangerous in systems with systemd since the cgroup
can be modified by systemd and cause issues to jobs.
.IP

.TP
\fBIgnoreSystemdOnFailure\fR=\fI<yes|no>\fR
Only for cgroup/v2 and for development and testing. It has similar functionality
to \fBIgnoreSystemd\fR but only in the case that a dbus call does not succeed.
.IP

.TP
\fBEnableControllers\fR=\fI<yes|no>\fR
Only for cgroup/v2 and generally for development, testing, when running on old
kernels and/or old systemd versions (e.g. RHEL8, systemd < 244) where not all
the controllers are enabled in the cgroup tree. With this parameter, slurmd gets
the available controllers from root's cgroup.controllers file
(\fBCgroupMountPoint\fR, by default /sys/fs/cgroup/cgroup.controllers) and makes
them available in all levels of the cgroup tree until it reaches Slurm's cgroup
leaf.
.IP

.SH "TASK/CGROUP PLUGIN"

.LP
The following cgroup.conf parameters are defined to control the behavior
of this particular plugin:

.TP
\fBAllowedRAMSpace\fR=<number>
Constrain the job/step cgroup RAM to this percentage of the allocated memory.
The percentage supplied may be expressed as floating point number, e.g. 101.5.
Sets the cgroup soft memory limit at the allocated memory size and then sets the
job/step hard memory limit at the (AllowedRAMSpace/100) * allocated memory. If
the job/step exceeds the hard limit, then it might trigger Out Of Memory (OOM)
events (including oom\-kill) which will be logged to kernel log ring buffer
(dmesg in Linux). Setting AllowedRAMSpace above 100 may cause system Out of
Memory (OOM) events as it allows job/step to allocate more memory than
configured to the nodes. Reducing configured node available memory to avoid
system OOM events is suggested. Setting AllowedRAMSpace below 100 will result
in jobs receiving less memory than allocated and soft memory limit will set to
the same value as the hard limit.
Also see \fBConstrainRAMSpace\fR.
The default value is 100.
.IP

.TP
\fBAllowedSwapSpace\fR=<number>
Constrain the job cgroup swap space to this percentage of the allocated
memory. The default value is 0, which means that RAM+Swap will be limited
to \fBAllowedRAMSpace\fR. The supplied percentage may be expressed as a
floating point number, e.g. 50.5. If the limit is exceeded, the job steps
will be killed and a warning message will be written to standard error.
Also see \fBConstrainSwapSpace\fR.
\fBNOTE\fR: Setting AllowedSwapSpace to 0 does not restrict the Linux kernel
from using swap space. To control how the kernel uses swap space, see
\fBMemorySwappiness\fR.
.IP

.TP
\fBConstrainCores\fR=<yes|no>
If configured to "yes" then constrain allowed cores to the subset of
allocated resources. This functionality makes use of the cpuset subsystem.
Due to a bug fixed in version 1.11.5 of HWLOC, the task/affinity plugin may be
required in addition to task/cgroup for this to function properly.
The default value is "no".
.IP

.TP
\fBConstrainDevices\fR=<yes|no>
If configured to "yes" then constrain the job's allowed devices based on GRES
allocated resources. It uses the devices subsystem for that.
The default value is "no".
.IP

.TP
\fBConstrainRAMSpace\fR=<yes|no>
If configured to "yes" then constrain the job's RAM usage by setting
the memory soft limit to the allocated memory and the hard limit to
the allocated memory * \fBAllowedRAMSpace\fR. The default value is "no", in
which case the job's RAM limit will be set to its swap space limit if
\fBConstrainSwapSpace\fR is set to "yes". CR_*_Memory must be set in slurm.conf
for this parameter to take any effect.
Also see \fBAllowedSwapSpace\fR, \fBAllowedRAMSpace\fR and
\fBConstrainSwapSpace\fR.

\fBNOTE\fR: When using \fBConstrainRAMSpace\fR, if the combined memory used
by all processes in a step is greater than the limit, then the kernel will
trigger an OOM event, killing one or more of the processes in the step. The
step state will be marked as OOM, but the step itself will keep running and
other processes in the step may continue to run as well.
This differs from the behavior of \fBOverMemoryKill\fR, where the whole step
will be killed/cancelled.

\fBNOTE\fR: When enabled, ConstrainRAMSpace can lead to a noticeable decline in
per\-node job throughout. Sites with high\-throughput requirements should
carefully weigh the tradeoff between per\-node throughput, versus potential
problems that can arise from unconstrained memory usage on the node. See
<https://slurm.schedmd.com/high_throughput.html> for further discussion.
.IP

.TP
\fBConstrainSwapSpace\fR=<yes|no>
If configured to "yes" then constrain the job's swap space usage.
The default value is "no". Note that when set to "yes" and
ConstrainRAMSpace is set to "no", \fBAllowedRAMSpace\fR is automatically set
to 100% in order to limit the RAM+Swap amount to 100% of job's requirement
plus the percent of allowed swap space. This amount is thus set to both
RAM and RAM+Swap limits. This means that in that particular case,
ConstrainRAMSpace is automatically enabled with the same limit as the one
used to constrain swap space. CR_*_Memory must be set in slurm.conf
for this parameter to take any effect.
Also see \fBAllowedSwapSpace\fR.
.IP

.TP
\fBMaxRAMPercent\fR=\fIPERCENT\fR
Set an upper bound in percent of total RAM (configured RealMemory of the node)
on the RAM constraint for a job. This will be the memory constraint applied to
jobs that are not explicitly allocated memory by Slurm (i.e. Slurm's select
plugin is not configured to manage memory allocations). The \fIPERCENT\fR may
be an arbitrary floating point number. The default value is 100.
.IP

.TP
\fBMaxSwapPercent\fR=\fIPERCENT\fR
Set an upper bound (in percent of total RAM, configured RealMemory of the node)
on the amount of RAM+Swap that may be used for a job. This will be the swap
limit applied to jobs on systems where memory is not being explicitly allocated
to job. The \fIPERCENT\fR may be an arbitrary floating point number between 0
and 100. The default value is 100.
.IP

.TP
\fBMemorySwappiness\fR=<number>
Only for cgroup/v1.
Configure the kernel's priority for swapping out anonymous pages (such as
program data) verses file cache pages for the job cgroup. Valid values are
between 0 and 100, inclusive. A value of 0 prevents the kernel from swapping
out program data. A value of 100 gives equal priority to swapping out file
cache or anonymous pages. If not set, then the kernel's default swappiness
value will be used. \fBConstrainSwapSpace\fR
must be set to \fByes\fR in order for this parameter to be applied.
.IP

.TP
\fBMinRAMSpace\fR=<number>
Set a lower bound (in MB) on the memory limits defined by
\fBAllowedRAMSpace\fR and \fBAllowedSwapSpace\fR. This prevents
accidentally creating a memory cgroup with such a low limit that slurmstepd
is immediately killed due to lack of RAM. The default limit is 30M.
.IP

.SH "PROCTRACK/CGROUP PLUGIN"

.LP
The following cgroup.conf parameters are defined to control the behavior
of this particular plugin:

.TP
\fBSignalChildrenProcesses\fR=<yes|no>
If configured to "yes", then send signals (for cancelling, suspending, resuming,
etc.) to all children processes in a job/step. Otherwise, only send signals to
the parent process of a job/step. The default setting is "no".
.IP

.SH "DISTRIBUTION\-SPECIFIC NOTES"

.LP
Debian and derivatives (e.g. Ubuntu) usually exclude the memory and memsw (swap)
cgroups by default. To include them, add the following parameters to the kernel
command line: \fBcgroup_enable=memory swapaccount=1\fR
.LP
This can usually be placed in /etc/default/grub inside the
\fBGRUB_CMDLINE_LINUX\fR variable. A command such as update\-grub must be run
after updating the file.

.SH "EXAMPLE"

.TP
\fB/etc/slurm/cgroup.conf\fR:
This example cgroup.conf file shows a configuration that enables the more
commonly used cgroup enforcement mechanisms.
.IP
.nf
###
# Slurm cgroup support configuration file.
###
ConstrainCores=yes
ConstrainDevices=yes
ConstrainRAMSpace=yes
ConstrainSwapSpace=yes
.fi

.TP
\fB/etc/slurm/slurm.conf\fR:
These are the entries required in \fBslurm.conf\fR to activate the cgroup
enforcement mechanisms. Make sure that the node definitions in your
\fBslurm.conf\fR closely match the configuration as shown by "\fBslurmd \-C\fR".
Either MemSpecLimit should be set or RealMemory should be defined with less
than the actual amount of memory for a node to ensure that all system/non\-job
processes will have sufficient memory at all times. Sites should also configure
\fBpam_slurm_adopt\fR to ensure users can not escape the cgroups via \fBssh\fR.
.IP
.nf
###
# Slurm configuration entries for cgroups
###
ProctrackType=proctrack/cgroup
TaskPlugin=task/cgroup,task/affinity
JobAcctGatherType=jobacct_gather/cgroup #optional for gathering metrics
PrologFlags=Contain                     #X11 flag is also suggested
.fi

.SH "COPYING"
Copyright (C) 2010\-2012 Lawrence Livermore National Security.
Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
.br
Copyright (C) 2010\-2022 SchedMD LLC.
.LP
This file is part of Slurm, a resource management program.
For details, see <https://slurm.schedmd.com/>.
.LP
Slurm is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your option)
any later version.
.LP
Slurm is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.

.SH "SEE ALSO"
.LP
\fBslurm.conf\fR(5)