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.. Copyright 2003-2025 by Wilson Snyder.
.. SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
verilator_gantt
===============
Verilator_gantt creates a visual representation to help analyze Verilator
multithreaded simulation performance by showing when each macro-task
starts, ends, and when each thread is busy or idle.
For an overview of the use of verilator_gantt, see :ref:`Profiling`.
Gantt Chart VCD
---------------
Verilated_gantt creates a value change dump (VCD) format dump file which
may be viewed in a waveform viewer (e.g., C<GTKWave>):
.. figure:: figures/fig_gantt_min.png
Example verilator_gantt output, as viewed with GTKWave.
The viewed waveform chart has time on the X-axis, with one unit for each
time tick of the system's high-performance counter.
Gantt Chart VCD Signals
-----------------------
In waveforms, there are the following signals. In GTKWave, use "decimal"
data format to remove the leading zeros and make the traces easier to read.
trace/section
Shows the name of the current top of the execution section stack.
Set GTKWave data format to "ASCII".
trace/depth
Shows the depth of the execution section stack.
Set GTKWave data format to "Analog".
measured_parallelism
The number of mtasks active at this time, for best performance, this will
match the thread count. In GTKWave, use a data format of "analog step" to
view this signal.
predicted_parallelism
The number of mtasks Verilator predicted would be active at this time,
for best performance this will match the thread count. In GTKWave, use a
data format of "analog step" to view this signal.
cpu#_thread
For the given CPU number, the thread number measured to be executing.
cpu#_waiting
For the given CPU number, aggregated waiting time for mtask dependencies.
Visualized as `X` values.
mtask#_cpu
For the given mtask id, the CPU it was measured to execute on.
thread#_mtask
For the given thread number, the mtask id it was executing.
predicted_thread#_mtask
For the given thread number, the mtask id Verilator predicted would be
executing.
verilator_gantt Example Usage
-----------------------------
..
verilator_gantt --help
verilator_gantt --version
verilator_gantt profile_exec.dat
verilator_gantt Arguments
-------------------------
.. program:: verilator_gantt
.. option:: <filename>
The filename to read data from; the default is "profile_exec.dat".
.. option:: --help
Displays a help summary, the program version, and exits.
.. option:: --no-vcd
Disables creating a .vcd file.
.. option:: --vcd <filename>
Sets the output filename for vcd dump; the default is "verilator_gantt.vcd".
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