2020-10-21 Triage Log
A variety of changes, nothing particularly notable from a performance perspective. #77792 is an interesting win on migrating to tracing values rather than the older log formatting. #76859 is also interesting, starting out as a functional fix but appears to have been a performance win for incremental benchmarks in some cases as well.
Triage done by @simulacrum. Revision range: 06a079c43efb062e335e6e6c9dabd3c750619980..22e6b9c68941996daa45786b4145e6196e51f0f4
4 Regressions, 7 Improvements, 0 Mixed 2 of them in rollups
Regressions
#77755
#77873
- Moderate regression in instruction counts (up to 2.7% on
full
builds of wg-grammar-check
) - Functional change. Regression not significantly major to warrant a revert.
#78060
- Moderate regression in instruction counts (up to 1.2% on
incr-unchanged
builds of clap-rs-check
) - Rollup; likely due to BTreeMap or meta-prelude changes. Not worth deep investigation: regression is minor and interesting changes are likely not readily changeable.
#77250
- Moderate regression in instruction counts (up to 3.1% on
incr-unchanged
builds of packed-simd-check
) - Functional change that we definitely want, performance regression is not too significant.
Improvements
#76859
- Very large improvement in instruction counts (up to -58.0% on
incr-patched: Compiler new
builds of regex-opt
) - Correctness is the key here, but it seems like our hand-rolled incremental tracking was (at least on the perf benchmarks) worse anyway.
#77792
- Moderate improvement in instruction counts (up to -1.7% on
incr-unchanged
builds of deeply-nested-async-opt
) - Switching to tracing spans and tracing‘s “values” over string-formatting seems to have been a improvement here. Definitely an interesting result -- presumably tracing’s handling is somehow more visible to LLVM?
#77796
- Moderate improvement in instruction counts (up to -1.4% on
full
builds of deeply-nested-async-check
) - Seems like potentially a slight regression on wall times, but ultimately the change is good on its merits, so no action is taken at this time.
#77947
- Large improvement in instruction counts (up to -7.4% on
incr-unchanged
builds of cranelift-codegen-debug
) - Seems to be a mixed result on wall times though.
#77373
- Moderate improvement in instruction counts (up to -1.6% on
full
builds of deeply-nested-async-check
) - Wall times are less positive, but mostly on incremental. Not deemed a concern.
#77908
#78151
- Large improvement in instruction counts (up to -7.6% on
incr-patched: println
builds of regression-31157-opt
)
Nags requiring follow up