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OpenDarwin 7.2.1 - man page for latency (opendarwin section 1)

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LATENCY(1)			   BSD 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
     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 argument, 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 USAGE
     latency -rt -st 20000 -it 1000 -l /var/tmp/latency.log

     The latency utility will set the realtime scheduling policy.  The threshold for the sched-
     uler is set to 20000 microseconds.  The threshold for interrupts is set to 1000 microsec-
     onds.  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
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