src/tools/cargo/src/doc/contrib/src/tests/profiling.md

   1 # Benchmarking and Profiling
   2
   3 ## Internal profiler
   4
   5 Cargo has a basic, hierarchical profiler built-in. The environment variable
   6 `CARGO_PROFILE` can be set to an integer which specifies how deep in the
   7 profile stack to print results for.
   8
   9 ```sh
  10 # Output first three levels of profiling info
  11 CARGO_PROFILE=3 cargo generate-lockfile
  12 ```
  13
  14 ## Benchmarking
  15
  16 ### Benchsuite
  17
  18 Head over to the [`benches`
  19 directory](https://github.com/rust-lang/cargo/tree/master/benches) for more
  20 information about the benchmarking suite.
  21
  22 ### Informal benchmarking
  23
  24 The overhead for starting a build should be kept as low as possible
  25 (preferably, well under 0.5 seconds on most projects and systems). Currently,
  26 the primary parts that affect this are:
  27
  28 * Running the resolver.
  29 * Querying the index.
  30 * Checking git dependencies.
  31 * Scanning the local project.
  32 * Building the unit dependency graph.
  33
  34 One way to test this is to use [hyperfine]. This is a tool that can be used to
  35 measure the difference between different commands and settings. Usually this
  36 is done by measuring the time it takes for `cargo build` to finish in a large
  37 project where the build is fresh (no actual compilation is performed). Just
  38 run `cargo build` once before using hyperfine.
  39
  40 [hyperfine]: https://github.com/sharkdp/hyperfine