Ubuntu Manpage: cgroup.conf - Slurm configuration file for the cgroup support

Provided by: slurm-client_21.08.5-2ubuntu2_amd64

NAME

       cgroup.conf - Slurm configuration file for the cgroup support

DESCRIPTION

cgroup.conf is an ASCII file which defines parameters used by Slurm's Linux cgroup related
plugins. The file location can be modified at system build time using the
DEFAULT_SLURM_CONF parameter or at execution time by setting the SLURM_CONF environment
variable. The file will always be located in the same directory as the slurm.conf file.

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.

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

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

CgroupAutomount=<yes|no>
Slurm cgroup plugins require valid and functional cgroup subsystem to be mounted
under /sys/fs/cgroup/<subsystem_name>. When launched, plugins check their
subsystem availability. If not available, the plugin launch fails unless
CgroupAutomount is set to yes. In that case, the plugin will first try to mount the
required subsystems.

CgroupMountpoint=PATH
Specify the PATH under which cgroups should be mounted. This should be a writable
directory which will contain cgroups mounted one per subsystem. The default PATH is
/sys/fs/cgroup.

CgroupPlugin=<cgroup/v1|autodetect>
Specify the plugin to be used when interacting with the cgroup subsystem.
Supported values at the moment are only "cgroup/v1" which supports the legacy
interface of cgroup v1, or "autodetect" which tries to determine which cgroup
version does your system provide. This is useful if nodes have support for
different cgroup versions. The default value is "autodetect".

TASK/CGROUP PLUGIN

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

AllowedKmemSpace=<number>
Constrain the job cgroup kernel memory to this amount of the allocated memory,
specified in bytes. The AllowedKmemSpace must be between the upper and lower memory
limits, specified by MaxKmemPercent and MinKmemSpace, respectively. If
AllowedKmemSpace goes beyond the upper or lower limit, it will be reset to that
upper or lower limit, whichever has been exceeded.

AllowedRAMSpace=<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 ConstrainRAMSpace. The default value is 100.

AllowedSwapSpace=<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
AllowedRAMSpace. 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 ConstrainSwapSpace.
NOTE: Setting AllowedSwapSpace to 0 does not restrict the Linux kernel from using
swap space. To control how the kernel uses swap space, see MemorySwappiness.

ConstrainCores=<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".

ConstrainDevices=<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".

ConstrainKmemSpace=<yes|no>
If configured to "yes" then constrain the job's Kmem RAM usage in addition to RAM
usage. Only takes effect if ConstrainRAMSpace is set to "yes". If enabled, the
job's Kmem limit will be assigned the value of AllowedKmemSpace or the value coming
from MaxKmemPercent. The default value is "no" which will leave Kmem setting
untouched by Slurm. Also see AllowedKmemSpace, MaxKmemPercent.

ConstrainRAMSpace=<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 *
AllowedRAMSpace. The default value is "no", in which case the job's RAM limit will
be set to its swap space limit if ConstrainSwapSpace is set to "yes". Also see
AllowedSwapSpace, AllowedRAMSpace and ConstrainSwapSpace.

NOTE: When using ConstrainRAMSpace, 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 OverMemoryKill, where
the whole step will be killed/cancelled.

NOTE: 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.

ConstrainSwapSpace=<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",
AllowedRAMSpace 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. Also see AllowedSwapSpace.

MaxRAMPercent=PERCENT
Set an upper bound in percent of total RAM 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 PERCENT may be an arbitrary floating point number. The default
value is 100.

MaxSwapPercent=PERCENT
Set an upper bound (in percent of total RAM) 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 PERCENT may be an arbitrary floating
point number between 0 and 100. The default value is 100.

MaxKmemPercent=PERCENT
Set an upper bound in percent of total RAM as the maximum Kmem for a job. The
PERCENT may be an arbitrary floating point number, however, the product of
MaxKmemPercent and job requested memory has to fall between MinKmemSpace and job
requested memory, otherwise the boundary value is used. The default value is 100.

MemorySwappiness=<number>
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.
ConstrainSwapSpace must be set to yes in order for this parameter to be applied.

MinKmemSpace=<number>
Set a lower bound (in MB) on the memory limits defined by AllowedKmemSpace. The
default limit is 30M.

MinRAMSpace=<number>
Set a lower bound (in MB) on the memory limits defined by AllowedRAMSpace and
AllowedSwapSpace. 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.

DISTRIBUTION-SPECIFIC NOTES

       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:
       cgroup_enable=memory swapaccount=1

       This can usually be placed in /etc/default/grub inside the GRUB_CMDLINE_LINUX variable.  A
       command such as update-grub must be run after updating the file.

EXAMPLE

       /etc/slurm/cgroup.conf:
              This  example cgroup.conf file shows a configuration that enables the more commonly
              used cgroup enforcement mechanisms.

              ###
              # Slurm cgroup support configuration file.
              ###
              CgroupAutomount=yes
              CgroupMountpoint=/sys/fs/cgroup
              ConstrainCores=yes
              ConstrainDevices=yes
              ConstrainKmemSpace=no        #avoid known Kernel issues
              ConstrainRAMSpace=yes
              ConstrainSwapSpace=yes

       /etc/slurm/slurm.conf:
              These are the entries required in slurm.conf to  activate  the  cgroup  enforcement
              mechanisms.  Make  sure  that the node definitions in your slurm.conf closely match
              the configuration as shown by "slurmd -C".  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 pam_slurm_adopt to ensure users can not escape
              the cgroups via ssh.

              ###
              # 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

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