2020-11-10.md

2020-11-10 Triage Log

A mixed week with improvements still outweighing regressions. Perhaps the biggest highlight was the move to compiling rustc crates with the initial-exec TLS model which results in fewer calls to _tls_get_addr and thus faster compile times.

Triage done by @rylev. Revision range: 5cdf5b882da9e8b7c73b5cadeb7745cb68f6ff63..cf9cf7c923eb01146971429044f216a3ca905e06

1 Regressions, 2 Improvements, 2 Mixed

Regressions

#78267

• Small regression in instruction counts (up to 1.2% on full builds of deeply-nested-async-check)
• This might be noise as this only affects one benchmark negatively, and that benchmark tends to be on the noisier side.

Improvements

#78280

• Moderate improvement in instruction counts (up to -1.3% on incr-patched: new row builds of tuple-stress-opt)

#78201

• Large improvement in instruction counts (up to -7.2% on incr-full builds of webrender-wrench-check)
• This change may produce similar performance gains in related tooling such as rustdoc and clippy.

Mixed

#77227

• Large improvement in instruction counts (up to -5.0% on incr-unchanged builds of deeply-nested-async-check)
• Moderate regression in instruction counts (up to 1.3% on full builds of ctfe-stress-4-check)

#78410

• Very large improvement in instruction counts (up to -26.0% on incr-unchanged builds of deeply-nested-async-opt)
• Moderate regression in instruction counts (up to 3.8% on full builds of ctfe-stress-4-check)
• This change is a revert of a previous change, and at least one user was reporting massive performance gains.

Nags requiring follow up

The compiler team is once again requested to look into:

• rust-lang/rust#78432 (comment)