LATENCY(1) BSD General Commands Manual LATENCY(1)

NAME
     llaatteennccyy - monitors scheduling and interrupt latency

SYNOPSIS
     llaatteennccyy [-rrtt] [-cc codefile] [-ll logfile] [-sstt threshold] [-iitt threshold]
             [-ss sleepinusecs] [-dd decrementerinusecs] [-nn kernel]

DESCRIPTION
     The llaatteennccyy 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:

     -rrtt     Set real time scheduling policy.  Default policy is timeshare.

     -cc      When the -cc 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.

     -ll      Specifies a logfile that is written to when either the interrupt
             or scheduling latency is exceeded.

     -sstt     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.

     -iitt     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.

     -ss      The -ss option sets the timer.  It takes microseconds as an argu-
             ment, the default timer is set to 1000 microseconds.

     -dd      The -dd option sets the decrementer.  It takes microseconds as an
             argument.  The decrementer is set back to the system default on
             exit.

     -nn      By default, llaatteennccyy acts on the default /machkernel.  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 llaatteennccyy utility is also SIGWINCH savvy, so adjusting your window
     geometry will change the list of delay values displayed.

SSAAMMPPLLEE UUSSAAGGEE
     latency -rt -st 20000 -it 1000 -l /var/tmp/latency.log

     The llaatteennccyy 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 ALSO
     top(1), fsusage(1), scusage(1)

Mac OS X                        March 28, 2000                        Mac OS X