.Op Fl d Ar decrementer_in_usecs
.Op Fl n Ar kernel
.Sh DESCRIPTION
+The
.Nm latency
-provides scheduling and interrupt latency statistics.
+utility provides scheduling and interrupt latency statistics.
+It requires root privileges due to the kernel tracing facility it uses to
+operate.
.Pp
The arguments are as follows:
.Bl -tag -width Ds
.It Fl rt
-Set real time scheduling policy. Default policy is timeshare.
+Set real time scheduling policy.
+Default policy is timeshare.
.It Fl c
When the
.Fl c
option is specified, it takes a path to a
.Ar 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.
+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.
.It Fl l
Specifies a
.Ar logfile
-that is written to when either the interrupt or scheduling
-latency is exceeded.
+that is written to when either the interrupt or scheduling latency is exceeded.
.It Fl 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.
+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 Fl 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.
+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.
.It Fl s
The
.Fl s
-option sets the timer. It takes microseconds as an argument,
-the default timer is set to 1000 microseconds.
+option sets the timer.
+It takes microseconds as an argument, the default timer is set to 1000
+microseconds.
.It Fl d
The
.Fl d
-option sets the decrementer. It takes microseconds as an argument.
+option sets the decrementer.
+It takes microseconds as an argument.
The decrementer is set back to the system default on exit.
.It Fl n
By default,
.Nm latency
-acts on the default /mach_kernel. This option
-allows you to specify an alternate booted kernel.
+acts on the default /mach_kernel.
+This option allows you to specify an alternate booted kernel.
.El
.Pp
The data columns displayed are as follows:
.Bl -tag -width LAST_PATHNAME_WAITED_FOR -compact
.Pp
.It SCHEDULER
-The number of context switches that fall
-within the described delay.
+The number of context switches that fall within the described delay.
.It INTERRUPTS
-The number of interrupts that fall
-within the described delay.
+The number of interrupts that fall within the described delay.
.El
.Pp
The
.Nm latency
-command is also SIGWINCH savvy, so adjusting your window geometry will change
+utility is also SIGWINCH savvy, so adjusting your window geometry will change
the list of delay values displayed.
.Sh SAMPLE USAGE
.Pp
latency -rt -st 20000 -it 1000 -l /var/tmp/latency.log
.Pp
+The
.Nm 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.
+utility 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.
.Sh SEE ALSO
-.Xr top 1
-.Xr fs_usage 1
+.Xr top 1 ,
+.Xr fs_usage 1 ,
.Xr sc_usage 1
projects / apple / system_cmds.git / blobdiff