trace - show or dump the tracing info

  trace [ <show [-c <cpulist>] [-f [no]<flagname>]> | <dump [-sm] <dest-dir>> ]


trace show
    shows all events with readability text(sorted by timestamp)

trace report
    the same as "trace show"

trace dump [-sm] <dest-dir>
    dump ring_buffers to dest-dir. Then you can parse it
    by other tracing tools. The dirs and files are generated
    the same as debugfs/tracing.
    -m: also dump metadata of ftrace.
    -s: also dump symbols of the kernel.

trace dump -t [output-file-name]
   dump ring_buffers and all meta data to a file that can
   be parsed by trace-cmd. Default output file name is "trace.dat".