IRQBALANCE(1)                     irqbalance                     IRQBALANCE(1)

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


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

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

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

       -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 addative 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

              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-

       The default value for deepestcache is 2.

       -l, --policyscript=<script>
              When specified, the referenced script 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.   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 interpreted 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.

              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
              devices  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.

       -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.

              Same as --oneshot.

              Same as --debug.

              Provides a mask of CPUs which irqbalance should ignore and never
              assign interrupts to.

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

       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

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


Linux                              Dec 2006                      IRQBALANCE(1)
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