.Nd monitors scheduling and interrupt latency
.Sh SYNOPSIS
.Nm latency
-.Op Fl rt
-.Op Fl c Ar codefile
-.Op Fl l Ar logfile
+.Op Fl p Ar priority
+.Op Fl h
+.Op Fl m
.Op Fl st Ar threshold
.Op Fl it Ar threshold
-.Op Fl s Ar sleep_in_usecs
-.Op Fl d Ar decrementer_in_usecs
+.Op Fl c Ar code_file
+.Op Fl l Ar log_file
+.Op Fl R Ar raw_file
.Op Fl n Ar kernel
.Sh DESCRIPTION
The
.Nm latency
-utility provides scheduling and interrupt latency statistics.
-It requires root privileges due to the kernel tracing facility it uses to
-operate.
+utility provides scheduling and interrupt-latency statistics.
+Due to the kernel tracing facility it uses to operate,
+the command requires root privileges.
.Pp
The arguments are as follows:
.Bl -tag -width Ds
-.It Fl rt
-Set real time scheduling policy.
-Default policy is timeshare.
-.It Fl c
+.\" ==========
+.It Fl c Ar code_file
When the
.Fl c
-option is specified, it takes a path to a
-.Ar codefile
+option is specified, it takes a path to a code file
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.
-.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.
-.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.
-.It Fl s
-The
-.Fl s
-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.
-The decrementer is set back to the system default on exit.
-.It Fl n
+This option overrides the default location of the system call code file,
+which is found in /usr/share/misc/trace.codes.
+.\" ==========
+.It Fl h
+Display high resolution interrupt latencies and write them to latencies.csv (truncate existing file) upon exit.
+.\" ==========
+.It Fl m
+Display per-CPU interrupt latency statistics.
+.\" ==========
+.It Fl it Ar threshold
+Set the interrupt latency threshold,
+expressed in microseconds.
+If the latency exceeds this value,
+and a log file has been specified,
+a record of what occurred during this time is recorded.
+.\" ==========
+.It Fl l Ar log_file
+Specifies a log file that is written to when
+either the interrupt or scheduling latency is exceeded.
+.\" ==========
+.It Fl n Ar kernel
By default,
.Nm latency
-acts on the default /mach_kernel.
+acts on the default /System/Library/Kernels/kernel.development.
This option allows you to specify an alternate booted kernel.
+.\" ==========
+.It Fl p Ar priority
+Specifies the priority level to observe scheduler latencies for.
+The default is realtime (
+.Ar 97
+). A range of priorities to monitor
+can also be provided, for example
+.Ar 31-47
+or
+.Ar 0-127
+.
+.\" ==========
+.It Fl st Ar threshold
+Set the scheduler latency threshold in microseconds.
+If latency exceeds this, and a log file has been specified,
+a record of what occurred during this time is recorded.
+.\" ==========
+.It Fl R Ar raw_file
+Specifies a raw trace file to use as input.
.El
.Pp
The data columns displayed are as follows:
-.Bl -tag -width LAST_PATHNAME_WAITED_FOR -compact
-.Pp
+.Bl -tag -width LAST_PATHNAME_WAITED_FOR
.It SCHEDULER
The number of context switches that fall within the described delay.
.It INTERRUPTS
the list of delay values displayed.
.Sh SAMPLE USAGE
.Pp
-latency -rt -st 20000 -it 1000 -l /var/tmp/latency.log
+latency -p 97 -st 20000 -it 1000 -l /var/tmp/latency.log
.Pp
The
.Nm latency
-utility will set the realtime scheduling policy.
+utility will watch threads with priority 97 for scheduling latencies.
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 sc_usage 1
+.Xr sc_usage 1 ,
+.Xr top 1
projects / apple / system_cmds.git / blobdiff