LATENCY(1)              System General Commands Manual              LATENCY(1)

NAME
     latency - monitors scheduling and interrupt latency

SYNOPSIS
     latency [-rt] [-c codefile] [-l logfile] [-st threshold] [-it threshold]
             [-s sleep_in_usecs] [-d decrementer_in_usecs] [-n kernel]

DESCRIPTION
     latency provides scheduling and interrupt latency statistics.

     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 command is also SIGWINCH savvy, so adjusting your window
     geometry will change the list of delay values displayed.

SAMPLE USAGE
     latency -rt -st 20000 -it 1000 -l /var/tmp/latency.log

     latency will set the realtime scheduling policy.  The threshold 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 ALSO
     top(1) fs_usage(1) sc_usage(1)

Mac OS X                        March 28, 2000                        Mac OS X