jobserver is used at run time in 160 crates (of which 16 optionally, 10 directly). It's used at build time in 1,003 crates (of which 277 optionally, 1 directly). It's used only as a dev dependency in 54 crates.

Depender (with downloads and own rev deps) jobserver version
1.6M 872 cc optional ^0.1.16
25K 18 rustc-ap-rustc_data_structures ^0.1.13
24K 74 cargo ^0.1.21
5.6K sccache ^0.1
3.7K 10 opencv build ^0.1
1.7K build-parallel ^0.1.19
270 1 hal ^0.1.11
cargo-semverver ^0.1.11
10 fast-rustc-ap-rustc_data_structures ^0.1.13
5 msiz_rustc-ap-rustc_data_structures ^0.1.13
vkcargo ^0.1.21