IRQBALANCE(1) irqbalance IRQBALANCE(1)
irqbalance - distribute hardware interrupts across processors on a mul-
The purpose of irqbalance is to distribute hardware interrupts across
processors on a multiprocessor system in order to increase performance.
Causes irqbalance to be run once, after which the daemon exits.
Causes irqbalance to print extra debug information. Implies
Causes irqbalance to run in the foreground (without --debug).
Enables log output optimized for systemd-journal.
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.
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
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.
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.
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.
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
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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