LATENCY(1) BSD General Commands Manual LATENCY(1)NAMElatency — monitors scheduling and interrupt latencySYNOPSISlatency [-rt] [-c codefile] [-l logfile] [-st threshold] [-it threshold]
[-s sleep_in_usecs] [-d decrementer_in_usecs] [-n kernel]
DESCRIPTION
The latency utility provides scheduling and interrupt latency statistics.
It requires root privileges due to the kernel tracing facility it uses to
operate.
The arguments are as follows:
-rt Set real time scheduling policy. Default policy is timeshare.
-c When the -c option is specified, it takes a path to a codefile
that contains the mappings for the system calls. This option
overrides the default location of the system call codefile which
is found in /usr/share/misc/trace.codes.
-l Specifies a logfile that is written to when either the interrupt
or scheduling latency is exceeded.
-st Set the scheduler latency threshold in microseconds. If latency
exceeds this, and a logfile has been specified, a record of what
occurred during this time is recorded.
-it Set the interrupt latency threshold in microseconds. If latency
exceeds this, and a logfile has been specified, a record of what
occurred during this time is recorded.
-s The -s option sets the timer. It takes microseconds as an argu‐
ment, the default timer is set to 1000 microseconds.
-d The -d option sets the decrementer. It takes microseconds as an
argument. The decrementer is set back to the system default on
exit.
-n By default, latency acts on the default /mach_kernel. This
option allows you to specify an alternate booted kernel.
The data columns displayed are as follows:
SCHEDULER The number of context switches that fall within
the described delay.
INTERRUPTS The number of interrupts that fall within the
described delay.
The latency utility is also SIGWINCH savvy, so adjusting your window
geometry will change the list of delay values displayed.
SAMPLE USAGElatency-rt -st 20000 -it 1000 -l /var/tmp/latency.log
The latency utility will set the realtime scheduling policy. The thresh‐
old for the scheduler is set to 20000 microseconds. The threshold for
interrupts is set to 1000 microseconds. Latencies that exceed these
thresholds will be logged in /var/tmp/latency.log.
SEE ALSOtop(1), fs_usage(1), sc_usage(1)Mac OS X March 28, 2000 Mac OS X