NAME

       verilator_gantt - Create Gantt chart of multi-threaded execution

SYNOPSIS

       Creates a visual representation to help analyze Verilator multithreaded simulation
       performance, by showing when each macro-task starts and ends, and showing when each thread
       is busy or idle.

       The generated Gantt chart has time on the X-axis. Times shown are to the scale printed,
       i.e. a certain about of time for each character width.  The Y-axis shows threads, each
       thread's execution is shown on one line.  That line shows "[" at the position in time when
       it executes.

       Following the "[" is the cpu number the task executed on, followed by zero or more "-" to
       make the width of the characters match the scaled execution time, followed by a "]".  If
       the scale is too small, the cpu number and mtask number will not be printed.  If the scale
       is very small, a "&" indicates multiple mtasks started at that time position.

       Also creates a value change dump (VCD) format dump file which may be viewed in a waveform
       viewer (e.g. "GTKWave").  See below.

USAGE

         Build with --prof-threads.

         Run a sim with +verilator+prof+threads+window 2.

         This will create profile_threads.dat.

         Then run:

         verilator_gantt profile_threads.dat

         The report will be printed on standard output, this also generates
         profile_threads.vcd

         View profile_threads.vcd in a waveform viewer.

VCD SIGNALS

       In waveforms there are the following signals. Most signals the "decimal" format will
       remove the leading zeros and make the traces easier to read.

       parallelism: The number of mtasks active at this time, for best performance this will
       match the thread count. You may want to use an "analog step" format to view this signal.

       cpu#_thread: For the given CPU number, the thread number executing.

       mtask#_cpu; For the given mtask id, the CPU it is executing on.

       thread#_mtask: For the given thread number, the mtask id executing.

ARGUMENTS

       filename
           The filename to read data from, defaults to "profile_threads.dat".

       --help
           Displays this message and program version and exits.

       --scale n
           On the X-axis of the generated Gantt chart, each character represents this many time
           units. (On x86, time units are rdtsc ticks.)  Defaults to 0, which will automatically
           compute a reasonable scale where no two mtasks need to fit into same character width's
           worth of scaled time.

       --no-vcd
       --vcd filename
           Set output filename for vcd dump, or disable. Default is verilator_gantt.vcd.

DISTRIBUTION

       The latest version is available from <https://verilator.org>.

       Copyright 2018-2020 by Wilson Snyder. This program is free software; you can redistribute
       it and/or modify it under the terms of either the GNU Lesser General Public License
       Version 3 or the Perl Artistic License Version 2.0.

       SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0

AUTHORS

       Wilson Snyder <wsnyder@wsnyder.org>

SEE ALSO

       "verilator"