-p tracer
Specify a tracer. Tracers usually do more than just trace an
event. Common tracers are: function, function_graph,
preemptirqsoff, irqsoff, preemptoff and wakeup. A tracer must
be supported by the running kernel. To see a list of
available tracers, see trace-cmd-list(1).
-e event
Specify an event to trace. Various static trace points have
been added to the Linux kernel. They are grouped by subsystem
where you can enable all events of a given subsystem or
specify specific events to be enabled. The event is of the
format "subsystem:event-name". You can also just specify the
subsystem without the :event-name or the event-name without
the "subsystem:". Using "-e sched_switch" will enable the
"sched_switch" event where as, "-e sched" will enable all
events under the "sched" subsystem.
The 'event' can also contain glob expressions. That is, "*stat*" will
select all events (or subsystems) that have the characters "stat" in their
names.
The keyword 'all' can be used to enable all events.
-a
Every event that is being recorded has its output format file
saved in the output file to be able to display it later. But
if other events are enabled in the trace without trace-cmd's
knowledge, the formats of those events will not be recorded
and trace-cmd report will not be able to display them. If
this is the case, then specify the -a option and the format
for all events in the system will be saved.
-T
Enable a stacktrace on each event. For example:
<idle>-0 [003] 58549.289091: sched_switch: kworker/0:1:0 [120] R ==> trace-cmd:2603 [120]
<idle>-0 [003] 58549.289092: kernel_stack: <stack trace>
=> schedule (ffffffff814b260e)
=> cpu_idle (ffffffff8100a38c)
=> start_secondary (ffffffff814ab828)
--func-stack
Enable a stack trace on all functions. Note this is only
applicable for the "function" plugin tracer, and will only
take effect if the -l option is used and succeeds in limiting
functions. If the function tracer is not filtered, and the
stack trace is enabled, you can live lock the machine.
-f filter
Specify a filter for the previous event. This must come after
a -e. This will filter what events get recorded based on the
content of the event. Filtering is passed to the kernel
directly so what filtering is allowed may depend on what
version of the kernel you have. Basically, it will let you
use C notation to check if an event should be processed or
not.
==, >=, <=, >, <, &, |, && and ||
The above are usually safe to use to compare fields.
--no-filter
Do not filter out the trace-cmd threads. By default, the
threads are filtered out to not be traced by events. This
option will have the trace-cmd threads also be traced.
-R trigger
Specify a trigger for the previous event. This must come
after a -e. This will add a given trigger to the given event.
To only enable the trigger and not the event itself, then
place the event after the -v option.
See Documentation/trace/events.txt in the Linux kernel source for more
information on triggers.
-v
This will cause all events specified after it on the command
line to not be traced. This is useful for selecting a
subsystem to be traced but to leave out various events. For
Example: "-e sched -v -e "*stat\*"" will enable all events in
the sched subsystem except those that have "stat" in their
names.
Note: the *-v* option was taken from the way grep(1) inverts the following
matches.
-F
This will filter only the executable that is given on the
command line. If no command is given, then it will filter
itself (pretty pointless). Using -F will let you trace only
events that are caused by the given command.
-P pid
Similar to -F but lets you specify a process ID to trace.
-c
Used with either -F (or -P if kernel supports it) to trace
the process' children too.
--user
Execute the specified command as given user.
-C clock
Set the trace clock to "clock".
Use trace-cmd(1) list -C to see what clocks are available.
-o output-file
By default, trace-cmd report will create a trace.dat file.
You can specify a different file to write to with the -o
option.
-l function-name
This will limit the function and function_graph tracers to
only trace the given function name. More than one -l may be
specified on the command line to trace more than one
function. The limited use of glob expressions are also
allowed. These are match* to only filter functions that start
with match. *match to only filter functions that end with
match. *match\* to only filter on functions that contain
match.
-g function-name
This option is for the function_graph plugin. It will graph
the given function. That is, it will only trace the function
and all functions that it calls. You can have more than one
-g on the command line.
-n function-name
This has the opposite effect of -l. The function given with
the -n option will not be traced. This takes precedence, that
is, if you include the same function for both -n and -l, it
will not be traced.
-d
Some tracer plugins enable the function tracer by default.
Like the latency tracers. This option prevents the function
tracer from being enabled at start up.
-D
The option -d will try to use the function-trace option to
disable the function tracer (if available), otherwise it
defaults to the proc file: /proc/sys/kernel/ftrace_enabled,
but will not touch it if the function-trace option is
available. The -D option will disable both the ftrace_enabled
proc file as well as the function-trace option if it exists.
Note, this disable function tracing for all users, which includes users
outside of ftrace tracers (stack_tracer, perf, etc).
-O option
Ftrace has various options that can be enabled or disabled.
This allows you to set them. Appending the text no to an
option disables it. For example: "-O nograph-time" will
disable the "graph-time" Ftrace option.
-s interval
The processes that trace-cmd creates to record from the ring
buffer need to wake up to do the recording. Setting the
interval to zero will cause the processes to wakeup every
time new data is written into the buffer. But since Ftrace is
recording kernel activity, the act of this processes going
back to sleep may cause new events into the ring buffer which
will wake the process back up. This will needlessly add extra
data into the ring buffer.
The 'interval' metric is microseconds. The default is set to 1000 (1 ms).
This is the time each recording process will sleep before waking up to
record any new data that was written to the ring buffer.
-r priority
The priority to run the capture threads at. In a busy system
the trace capturing threads may be staved and events can be
lost. This increases the priority of those threads to the
real time (FIFO) priority. But use this option with care, it
can also change the behaviour of the system being traced.
-b size
This sets the ring buffer size to size kilobytes. Because the
Ftrace ring buffer is per CPU, this size is the size of each
per CPU ring buffer inside the kernel. Using "-b 10000" on a
machine with 4 CPUs will make Ftrace have a total buffer size
of 40 Megs.
-B buffer-name
If the kernel supports multiple buffers, this will add a
buffer with the given name. If the buffer name already
exists, that buffer is just reset and will not be deleted at
the end of record execution. If the buffer is created, it
will be removed at the end of execution (unless the -k is
set, or start command was used).
After a buffer name is stated, all events added after that will be
associated with that buffer. If no buffer is specified, or an event
is specified before a buffer name, it will be associated with the
main (toplevel) buffer.
trace-cmd record -e sched -B block -e block -B time -e timer sleep 1
The above is will enable all sched events in the main buffer. It will
then create a 'block' buffer instance and enable all block events within
that buffer. A 'time' buffer instance is created and all timer events
will be enabled for that event.
-m size
The max size in kilobytes that a per cpu buffer should be.
Note, due to rounding to page size, the number may not be
totally correct. Also, this is performed by switching between
two buffers that are half the given size thus the output may
not be of the given size even if much more was written.
Use this to prevent running out of diskspace for long runs.
-M cpumask
Set the cpumask for to trace. It only affects the last buffer
instance given. If supplied before any buffer instance, then
it affects the main buffer. The value supplied must be a hex
number.
trace-cmd record -p function -M c -B events13 -e all -M 5
If the -M is left out, then the mask stays the same. To enable all
CPUs, pass in a value of '-1'.
-k
By default, when trace-cmd is finished tracing, it will reset
the buffers and disable all the tracing that it enabled. This
option keeps trace-cmd from disabling the tracer and reseting
the buffer. This option is useful for debugging trace-cmd.
Note: usually trace-cmd will set the "tracing_on" file back to what it
was before it was called. This option will leave that file set to zero.
-i
By default, if an event is listed that trace-cmd does not
find, it will exit with an error. This option will just
ignore events that are listed on the command line but are not
found on the system.
-N host:port
If another machine is running "trace-cmd listen", this option
is used to have the data sent to that machine with UDP
packets. Instead of writing to an output file, the data is
sent off to a remote box. This is ideal for embedded machines
with little storage, or having a single machine that will
keep all the data in a single repository.
Note: This option is not supported with latency tracer plugins:
wakeup, wakeup_rt, irqsoff, preemptoff and preemptirqsoff
-t
This option is used with -N, when there's a need to send the
live data with TCP packets instead of UDP. Although TCP is
not nearly as fast as sending the UDP packets, but it may be
needed if the network is not that reliable, the amount of
data is not that intensive, and a guarantee is needed that
all traced information is transfered successfully.
-q | --quiet
For use with recording an application. Suppresses normal
output (except for errors) to allow only the application's
output to be displayed.
--date
With the --date option, "trace-cmd" will write timestamps
into the trace buffer after it has finished recording. It
will then map the timestamp to gettimeofday which will allow
wall time output from the timestamps reading the created
trace.dat file.
--max-graph-depth depth
Set the maximum depth the function_graph tracer will trace
into a function. A value of one will only show where
userspace enters the kernel but not any functions called in
the kernel. The default is zero, which means no limit.
--cmdlines-size size
Set the number of entries the kernel tracing file
"saved_cmdlines" can contain. This file is a circular buffer
which stores the mapping between cmdlines and PIDs. If full,
it leads to unresolved cmdlines ("<...>") within the trace.
The kernel default value is 128.
--module module
Filter a module's name in function tracing. It is equivalent
to adding :mod:module after all other functions being
filtered. If no other function filter is listed, then all
modules functions will be filtered in the filter.
'--module snd' is equivalent to '-l :mod:snd'
'--module snd -l "*jack*"' is equivalent to '-l "*jack*:mod:snd"'
'--module snd -n "*"' is equivalent to '-n :mod:snd'
--proc-map
Save the traced process address map into the trace.dat file.
The traced processes can be specified using the option -P, or
as a given command.
--profile
With the --profile option, "trace-cmd" will enable tracing
that can be used with trace-cmd-report(1) --profile option.
If a tracer -p is not set, and function graph depth is
supported by the kernel, then the function_graph tracer will
be enabled with a depth of one (only show where userspace
enters into the kernel). It will also enable various
tracepoints with stack tracing such that the report can show
where tasks have been blocked for the longest time.
See trace-cmd-profile(1) for more details and examples.
-G
Set interrupt (soft and hard) events as global (associated to
CPU instead of tasks). Only works for --profile.
-H event-hooks
Add custom event matching to connect any two events together.
When not used with --profile, it will save the parameter and
this will be used by trace-cmd report --profile, too. That
is:
trace-cmd record -H hrtimer_expire_entry,hrtimer/hrtimer_expire_exit,hrtimer,sp
trace-cmd report --profile
Will profile hrtimer_expire_entry and hrtimer_expire_ext times.
See trace-cmd-profile(1) for format.
-S
(for --profile only) Only enable the tracer or events
speficied on the command line. With this option, the
function_graph tracer is not enabled, nor are any events
(like sched_switch), unless they are specifically specified
on the command line (i.e. -p function -e sched_switch -e
sched_wakeup)
--ts-offset offset
Add an offset for the timestamp in the trace.dat file. This
will add a offset option into the trace.dat file such that a
trace-cmd report will offset all the timestamps of the events
by the given offset. The offset is in raw units. That is, if
the event timestamps are in nanoseconds the offset will also
be in nanoseconds even if the displayed units are in
microseconds.
--tsync-interval
Set the loop interval, in ms, for timestamps synchronization
with guests: If a negative number is specified, timestamps
synchronization is disabled If 0 is specified, no loop is
performed - timestamps offset is calculated only twice," at
the beginning and at the end of the trace. Timestamps
synchronization with guests works only if there is support
for VSOCK.\n"
--stderr
Have output go to stderr instead of stdout, but the output of
the command executed will not be changed. This is useful if
you want to monitor the output of the command being executed,
but not see the output from trace-cmd.
