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tracing-coz

Rust-tracing support for the coz Causal Profiler

Documentation

Usage

First, follow the instructions in coz to install the coz command.

Note that this crate is a facade over rust-coz as such its information applies to this crate.

With this crate spans are mapped to coz::begin! and coz::end!, and events are mapped to coz::progress!, as throughput or latency tracepoints respectively. More information on this can be found upstream.

After you've instrumented your code, you need to also ensure that you're compiling with DWARF debug information. To do this you'll want to configure Cargo.toml again:

[profile.release]
debug = 1

Next up you'll build your application with cargo build --release, and then finally you can run it with coz run --- ./target/release/$your_binary.

Caveats

Known caveats so far to generate a report that collects information are:

  • Rust programs by default segfault when run with coz with an issue related to plasma-umass/coz#110. Rust programs set up a sigaltstack to run segfault handlers to print "you ran out of stack", but this alternate stack is too small to run the SIGPROF handler that coz installs. To handle this this crate provides a coz::thread_init() function which will increase the sigaltstack size that Rust installs by default to something large enough to run coz. If you see segfaults, or corrupt reports, you may wish to manually call coz::thread_init() instead of waiting for this crate to automatically call it for you, we export coz::thread_init() for convenience here.

  • Debug information looks to be critical to get a report from coz. Make sure that your program is compiled with at least line-table information (debug = 1) to ensure you get the best experience using coz.

  • Currently coz only works on Linux, and while this crate should compile on all platforms it only actually does something on Linux.

License

This project is licensed under either of

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.