LATENCY

Section: User Commands (1)
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BSD mandoc
Mac OS X  

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 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 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_usage1 sc_usage1


 

Index

NAME
SYNOPSIS
DESCRIPTION
SAMPLE USAGE
SEE ALSO

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Time: 04:29:23 GMT, April 24, 2025