forked from github/verilator
77 lines
2.4 KiB
ReStructuredText
77 lines
2.4 KiB
ReStructuredText
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.. Copyright 2003-2021 by Wilson Snyder.
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.. SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
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verilator_gantt
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===============
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Verilator_gantt creates a visual representation to help analyze Verilator
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multithreaded simulation performance, by showing when each macro-task
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starts and ends, and showing when each thread is busy or idle.
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For an overview of use of verilator_gantt, see :ref:`Profiling`.
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Gantt Chart Contents
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--------------------
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The generated Gantt chart has time on the X-axis. Times shown are to the
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scale printed, i.e. a certain about of time for each character width. The
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Y-axis shows threads, each thread's execution is shown on one line. That
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line shows "[" at the position in time when it executes.
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Following the "[" is the CPU number the task executed on, followed by zero
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or more "-" to make the width of the characters match the scaled execution
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time, followed by a "]". If the scale is too small, the CPU number and
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mtask number will not be printed. If the scale is very small, a "&"
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indicates multiple mtasks started at that time position.
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Also creates a value change dump (VCD) format dump file which may be viewed
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in a waveform viewer (e.g. C<GTKWave>). See below.
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Gantt Chart VCD Signals
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-----------------------
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In waveforms there are the following signals. Most signals the "decimal"
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format will remove the leading zeros and make the traces easier to read.
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parallelism
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The number of mtasks active at this time, for best performance this will
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match the thread count. You may want to use an "analog step" format to
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view this signal.
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cpu#_thread
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For the given CPU number, the thread number executing.
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mtask#_cpu
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For the given mtask id, the CPU it is executing on.
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thread#_mtask
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For the given thread number, the mtask id executing.
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verilator_gantt Arguments
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-------------------------
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.. program:: verilator_gantt
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.. option:: <filename>
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The filename to read data from, defaults to "profile_threads.dat".
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.. option:: --help
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Displays a help summary, the program version, and exits.
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.. option:: --scale <n>
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Sets the number of time units per character on the X-axis of the generated
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Gantt chart. (On x86, time units are rdtsc ticks.) Defaults to 0, which
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will automatically compute a reasonable scale where no two mtasks need to
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fit into same character width's worth of scaled time.
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.. option:: --no-vcd
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Disables creating a .vcd file.
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.. option:: --vcd <filename>
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Sets the output filename for vcd dump. Default is "verilator_gantt.vcd".
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