Debugging TVM

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Debugging TVM#

NOTE: This page is a work in-progress. Everyone is welcomed to add suggestions and tips via sending a PR to modify this page. The goal with this page is to centralize the commonly-used techniques being used to debug TVM and to spread awareness to the community. To that end, we may seek to promote more broadly-used techniques to the top of this doc.

VLOGging#

TVM provides a verbose-logging facility that allows you to commit trace-level debugging messages without impacting the binary size or runtime of TVM in production. You can use VLOG in your code as follows:

void Foo(const std::string& bar) {
  VLOG(2) << "Running Foo(" << bar << ")";
  // ...
}

In this example, the integer 2 passed to VLOG() indicates a verbosity level. The higher the level, the more logs printed. In general, TVM levels range from 0 to 2, with 3 being used only for extremely low-level core runtime properties. The VLOG system is configured at startup time to print VLOG statements between 0 and some integer N. N can be set per-file or globally.

VLOGs don't print or impact binary size or runtime by default (when compiled with proper optimization). To enable VLOGging, do the following:

  1. In config/cmake, ensure you set(USE_RELAY_DEBUG ON). This flag is used to enable VLOGging.

  2. Launch Python passing TVM_LOG_DEBUG=<spec>, where <spec>> is a comma-separated list of level assignments of the form <file_name>=<level>. Here are some specializations:

    • The special filename DEFAULT sets the VLOG level setting for all files.

    • <level> can be set to -1 to disable VLOG in that file.

    • <file_name> is the name of the c++ source file (e.g. .cc, not .h) relative to the src/ directory in the TVM repo. You do not need to supply src/ when specifying the file path, but if you do, VLOG will still interpret the path correctly.

Examples:

# enable VLOG(0), VLOG(1), VLOG(2) in all files.
$ TVM_LOG_DEBUG=DEFAULT=2 python3 -c 'import tvm'

# enable VLOG(0), VLOG(1), VLOG(2) in all files, except not VLOG(2) in src/bar/baz.cc.
$ TVM_LOG_DEBUG=DEFAULT=2,bar/baz.cc=1 python3 -c 'import tvm'

# enable VLOG(0), VLOG(1), VLOG(2) in all files, except not in src/foo/bar.cc.
$ TVM_LOG_DEBUG=DEFAULT=2,src/foo/bar.cc=-1 python3 -c 'import tvm'
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