crater very bad perf :3

[lcnr]

https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/crater.20triage.3A.20.60mathypad-core.60.20overflows/with/547985764

Benchmark 1: CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings
  Time (mean ± σ):      1.486 s ±  0.003 s    [User: 1.308 s, System: 0.188 s]
  Range (min … max):    1.484 s …  1.488 s    2 runs

Benchmark 2: CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings -Znext-solver
  Time (mean ± σ):     39.309 s ±  0.173 s    [User: 35.018 s, System: 4.296 s]
  Range (min … max):   39.186 s … 39.431 s    2 runs

Summary
  CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings  ran
   26.45 ± 0.13 times faster than CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings -Znext-solver

thx @lqd <3

[lcnr]

https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/crater.20triage.20.3A3/near/548148617

rows 111 and 112, databend-common-ast, crater logs

This doesn't reproduce on nightly either, only with the 149edce6c6ee840adb602803b96d083101ef3592 try build. We can look into it later then.

Here as well, compile times are of interest

> hyperfine -w1 -r2 -L args "","-Znext-solver" --setup "cargo clean" --prepare "touch src/lib.rs" "CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings {args}"

Benchmark 1: CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings
  Time (mean ± σ):     12.068 s ±  0.039 s    [User: 11.306 s, System: 0.771 s]
  Range (min … max):   12.040 s … 12.096 s    2 runs

Benchmark 2: CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings -Znext-solver
  Time (mean ± σ):     78.071 s ±  0.057 s    [User: 68.425 s, System: 9.649 s]
  Range (min … max):   78.031 s … 78.112 s    2 runs

Summary
  CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings  ran
    6.47 ± 0.02 times faster than CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings -Znext-solver

[lqd]

c2e in rows 94 and 95 also has interesting compile times

> hyperfine -w1 -r2 -L args "","-Znext-solver" --setup "cargo clean" --prepare "touch src/lib.rs" "CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings {args}"

Benchmark 1: CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings
  Time (mean ± σ):     981.9 ms ±  12.4 ms    [User: 852.1 ms, System: 139.2 ms]
  Range (min … max):   973.2 ms … 990.7 ms    2 runs

Benchmark 2: CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings -Znext-solver
  Time (mean ± σ):     13.348 s ±  0.050 s    [User: 12.677 s, System: 0.680 s]
  Range (min … max):   13.313 s … 13.383 s    2 runs

Summary
  CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings  ran
   13.59 ± 0.18 times faster than CARGO_INCREMENTAL=0 cargo rustc --profile check -- -Awarnings -Znext-solver