irqbalance

IRQBALANCE(1)                     irqbalance                     IRQBALANCE(1)

NAME
       irqbalance - distribute hardware interrupts across processors on a mul-
       tiprocessor system

SYNOPSIS
       irqbalance

DESCRIPTION
       The purpose of irqbalance is to distribute hardware  interrupts  across
       processors on a multiprocessor system in order to increase performance.

OPTIONS
       -o, --oneshot
              Causes irqbalance to be run once, after which the daemon exits.

       -d, --debug
              Causes  irqbalance  to  print  extra debug information.  Implies
              --foreground.

       -f, --foreground
              Causes irqbalance to run in the foreground (without --debug).

       -j, --journal
              Enables log output optimized for systemd-journal.

       -p, --powerthresh=<threshold>
              Set the threshold at which we attempt to move a CPU into  power-
              save mode If more than <threshold> CPUs are more than 1 standard
              deviation below the average CPU softirq workload,  and  no  CPUs
              are  more  than 1 standard deviation above (and have more than 1
              IRQ assigned to them), attempt to place 1 CPU in powersave mode.
              In  powersave mode, a CPU will not have any IRQs balanced to it,
              in an effort to prevent that CPU from waking up without need.

       -i, --banirq=<irqnum>
              Add the specified IRQ to the set of banned IRQs. irqbalance will
              not affect the affinity of any IRQs on the banned list, allowing
              them to be specified manually.  This option is additive and  can
              be  specified  multiple times. For example to ban IRQs 43 and 44
              from balancing,  use  the  following  command  line:  irqbalance
              --banirq=43 --banirq=44

       -m, --banmod=<module_name>
              Add  the  specified module to the set of banned modules, similar
              to --banirq.  irqbalance will not affect  the  affinity  of  any
              IRQs  of  given modules, allowing them to be specified manually.
              This option is additive and can be specified multiple times. For
              example  to  ban all IRQs of module foo and module bar from bal-
              ancing, use the following command line: irqbalance  --banmod=foo
              --banmod=bar

       -c, --deepestcache=<integer>
              This  allows  a user to specify the cache level at which irqbal-
              ance partitions cache domains.  Specifying a  deeper  cache  may
              allow  a  greater degree of flexibility for irqbalance to assign
              IRQ affinity to achieve greater performance increases, but  set-
              ting a cache depth too large on some systems (specifically where
              all CPUs on a system share the deepest cache level), will  cause
              irqbalance  to see balancing as unnecessary.  irqbalance --deep-
              estcache=2

       The default value for deepestcache is 2.

       -l, --policyscript=<script>
              When specified, the referenced script or directory will  execute
              once for each discovered IRQ, with the sysfs device path and IRQ
              number passed as arguments.  Note that the device path  argument
              will point to the parent directory from which the IRQ attributes
              directory may be directly opened.  Policy scripts specified need
              to be owned and executable by the user of irqbalance process, if
              a directory is specified, non-executable files will be  skipped.
              The  script  may  specify zero or more key=value pairs that will
              guide irqbalance in the management of that IRQ.  Key=value pairs
              are printed by the script on stdout and will be captured and in-
              terpreted by irqbalance.  Irqbalance expects a  zero  exit  code
              from the provided utility.  Recognized key=value pairs are:

       ban=[true | false]
              Directs irqbalance to exclude the passed in IRQ from balancing.

       balance_level=[none | package | cache | core]
              This allows a user to override the balance level of a given IRQ.
              By default the balance level is determined  automatically  based
              on the pci device class of the device that owns the IRQ.

       numa_node=<integer>
              This  allows  a  user to override the NUMA node that sysfs indi-
              cates a given device IRQ is local to.  Often, systems  will  not
              specify  this  information  in ACPI, and as a result devices are
              considered equidistant from all NUMA nodes in  a  system.   This
              option allows for that hardware provided information to be over-
              ridden, so that irqbalance can bias IRQ affinity for  these  de-
              vices  toward  its  most  local node.  Note that specifying a -1
              here forces irqbalance to consider an interrupt from a device to
              be equidistant from all nodes.

       Note  that, if a directory is specified rather than a regular file, all
       files in
              the directory will be considered policy scripts, and executed on
              adding  of  an irq to a database.  If such a directory is speci-
              fied, scripts in the directory must additionally exit  with  one
              of the following exit codes:

       0      This  indicates  the script has a policy for the referenced irq,
              and that further script processing should stop

       1      This indicates that the script has no policy for the  referenced
              irq, and that script processing should continue

       2      This  indicates that an error has occurred in the script, and it
              should be skipped (further processing to continue)

       -s, --pid=<file>
              Have irqbalance write its process id to the specified file.   By
              default no pidfile is written.  The written pidfile is automati-
              cally unlinked when irqbalance exits. It is  ignored  when  used
              with --debug or --foreground.

       -t, --interval=<time>
              Set  the measurement time for irqbalance.  irqbalance will sleep
              for <time> seconds between samples of the irq load on the system
              cpus. Defaults to 10.

ENVIRONMENT VARIABLES
       IRQBALANCE_ONESHOT
              Same as --oneshot.

       IRQBALANCE_DEBUG
              Same as --debug.

       IRQBALANCE_BANNED_CPUS
              Provides a mask of CPUs which irqbalance should ignore and never
              assign interrupts to.  If not specified, irqbalance use mask  of
              isolated  and  adaptive-ticks  CPUs on the system as the default
              value.

SIGNALS
       SIGHUP Forces a rescan of the available IRQs and system topology.

API
       irqbalance is able to communicate via socket and  return  it's  current
       assignment  tree  and  setup, as well as set new settings based on sent
       values. Socket is abstract, with a name in form of irqbalance<PID>.sock
       ,  where  <PID> is the process ID of irqbalance instance to communicate
       with.  Possible values to send:

       stats  Retrieve assignment tree of IRQs to CPUs, in  recursive  manner.
              For  each  CPU node in tree, it's type, number, load and whether
              the save mode is active are sent. For each  assigned  IRQ  type,
              it's  number,  load,  number  of IRQs since last rebalancing and
              it's class are sent. Refer to types.h file  for  explanation  of
              defines.

       setup  Get the current value of sleep interval, mask of banned CPUs and
              list of banned IRQs.

       settings sleep <s>
              Set new value of sleep interval, <s> >= 1.

       settings cpus <cpu_number1> <cpu_number2> ...
              Ban listed CPUs from IRQ handling, all old values of banned CPUs
              are forgotten.

       settings ban irqs <irq1> <irq2> ...
              Ban  listed  IRQs  from being balanced, all old values of banned
              IRQs are forgotten.

       irqbalance checks SCM_CREDENTIALS of sender (only root user is  allowed
       to  interact).   Based  on chosen tools, ancillary message with creden-
       tials needs to be sent with request.

HOMEPAGE
       https://github.com/Irqbalance/irqbalance

Linux                              Dec 2006                      IRQBALANCE(1)