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           trace-cmd record [OPTIONS] [command]


           The trace-cmd(1) record command will set up the Ftrace Linux kernel
           tracer to record the specified plugins or events that happen while the
           command executes. If no command is given, then it will record until the
           user hits Ctrl-C.
           The record command of trace-cmd will set up the Ftrace tracer to start
           tracing the various events or plugins that are given on the command
           line. It will then create a number of tracing processes (one per CPU)
           that will start recording from the kernel ring buffer straight into
           temporary files. When the command is complete (or Ctrl-C is hit) all
           the files will be combined into a trace.dat file that can later be read
           (see trace-cmd-report(1)).


           -p plugin
               Specify a trace plugin. Plugins are special Ftrace tracers that
               usually do more than just trace an event. Common plugins are
               function, function_graph, preemptirqsoff, irqsoff, preemptoff, and
               wakeup. A plugin must be supported by the running kernel. To see a
               list of available plugins, 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
                   The keyword 'all' can be used to enable all events.
           -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.
               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.
           -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
               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.
           -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).
               with 4 CPUs will make Ftrace have a total buffer size of 40 Megs.
           -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
               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.


           The basic way to trace all events:
                # trace-cmd record -e all ls > /dev/null
                # trace-cmd report
                      trace-cmd-13541 [003] 106260.693809: filemap_fault: address=0x128122 offset=0xce
                      trace-cmd-13543 [001] 106260.693809: kmalloc: call_site=81128dd4 ptr=0xffff88003dd83800 bytes_req=768 bytes_alloc=1024 gfp_flags=GFP_KERNEL|GFP_ZERO
                             ls-13545 [002] 106260.693809: kfree: call_site=810a7abb ptr=0x0
                             ls-13545 [002] 106260.693818: sys_exit_write:       0x1
           To use the function tracer with sched switch tracing:
                # trace-cmd record -p function -e sched_switch ls > /dev/null
                # trace-cmd report
                             ls-13587 [002] 106467.860310: function: hrtick_start_fair <-- pick_next_task_fair
                             ls-13587 [002] 106467.860313: sched_switch: prev_comm=trace-cmd prev_pid=13587 prev_prio=120 prev_state=R ==> next_comm=trace-cmd next_pid=13583 next_prio=120
                      trace-cmd-13585 [001] 106467.860314: function: native_set_pte_at <-- __do_fault
                      trace-cmd-13586 [003] 106467.860314: function:             up_read <-- do_page_fault
                             ls-13587 [002] 106467.860317: function:             __phys_addr <-- schedule
                      trace-cmd-13585 [001] 106467.860318: function: _raw_spin_unlock <-- __do_fault
                             ls-13587 [002] 106467.860320: function: native_load_sp0 <-- __switch_to
                      trace-cmd-13586 [003] 106467.860322: function: down_read_trylock <-- do_page_fault
           Here is a nice way to find what interrupts have the highest latency:
                # trace-cmd record -p function_graph -e irq_handler_entry  -l do_IRQ sleep 10
                # trace-cmd report
                         <idle>-0     [000] 157412.933969: funcgraph_entry:                  |  do_IRQ() {
                         <idle>-0     [000] 157412.933974: irq_handler_entry:    irq=48 name=eth0
                         <idle>-0     [000] 157412.934004: funcgraph_exit:       + 36.358 us |  }
                         <idle>-0     [000] 157413.895004: funcgraph_entry:                  |  do_IRQ() {
           trace-cmd-stop(1), trace-cmd-extract(1), trace-cmd-reset(1),
           trace-cmd-split(1), trace-cmd-list(1), trace-cmd-listen(1)


           Written by Steven Rostedt, <[1]>




           Copyright (C) 2010 Red Hat, Inc. Free use of this software is granted
           under the terms of the GNU Public License (GPL).


                                      12/03/2011               TRACE-CMD-RECORD(1)

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