Demonstrates exponential compile times in rust's tracing package.
The python script do_timing.py generates a module with a chain of 10 async
functions calling each other, and adds #[instrument] to n of these
functions. Then it compiles the package. Averaging over 10 compiles and
subtracting the compile time for 0 statements, we compile times that look
exponential in the number of #[instrument] statements (note the logarithmic y
axis):
If we replace #[instrument] by #[instrument(err)], compile times increase
drastically.
Removing async/await removes the slowdown, giving linear compile times (note the
linear y axis):
