rust-lang / rust-lang/rustc-perf
Suspicious time diff at https://perf.rust-lang.org/status.html in took/expected
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Description
Time displayed at https://perf.rust-lang.org/status.html for took/expected heavily differs for some runs, while perf result shows no difference.
For example, for run https://github.com/rust-lang/rust/pull/115388#issuecomment-1701235905
| Step | Took | Expected |
|---|---|---|
| await-call-tree | 0m28s | 0m28s |
| bitmaps-3.1.0 | 1m06s | 0m59s |
| cargo-0.60.0 | 8m24s | 5m23s |
| clap-3.1.6 | 1m43s | 1m32s |
| coercions | 0m56s | 0m54s |
| cranelift-codegen-0.82.1 | 9m50s | 3m02s |
| ctfe-stress-5 | 1m24s | 1m11s |
| deeply-nested-multi | 2m43s | 0m32s |
| deep-vector | 1m34s | 1m24s |
| derive | 4m13s | 0m49s |
| diesel-1.4.8 | 7m15s | 2m30s |
| exa-0.10.1 | 3m00s | 3m00s |
| externs | 0m38s | 0m39s |
| helloworld | 0m37s | 0m37s |
| helloworld-tiny | 0m11s | 0m11s |
| html5ever-0.26.0 | 1m18s | 1m08s |
| hyper-0.14.18 | 2m11s | 2m10s |
| image-0.24.1 | 2m00s | 2m01s |
| issue-46449 | 1m15s | 1m16s |
| issue-58319 | 0m32s | 0m32s |
| issue-88862 | 0m32s | 0m32s |
| libc-0.2.124 | 1m01s | 1m02s |
| many-assoc-items | 0m57s | 0m59s |
| match-stress | 0m51s | 0m52s |
| projection-caching | 0m41s | 0m41s |
| regex-1.5.5 | 2m58s | 2m56s |
| regression-31157 | 0m54s | 1m01s |
| ripgrep-13.0.0 | 2m04s | 2m02s |
| ripgrep-13.0.0-tiny | 1m05s | 1m04s |
| serde-1.0.136 | 1m33s | 1m33s |
| serde_derive-1.0.136 | 1m38s | 1m38s |
| stm32f4-0.14.0 | 3m49s | 6m10s |
| syn-1.0.89 | 1m28s | 1m24s |
| token-stream-stress | 0m28s | 0m32s |
| tt-muncher | 0m28s | 1m00s |
Notice cranelift, cargo, derive time diff for took/expected, while results clean https://perf.rust-lang.org/compare.html?start=b1b244da6527cf2ba36e88d02275f4c64a0c90d8&end=24259321f2e7a82959b47b86ded3d1073f281746&stat=instructions:u
And next perf for 6ff94474e1d11 (https://github.com/rust-lang/rust/pull/115391#issuecomment-1701488795) run bounces back:
| Step | Took | Expected |
|---|---|---|
| await-call-tree | 0m30s | 0m28s |
| bitmaps-3.1.0 | 1m02s | 1m06s |
| cargo-0.60.0 | 5m26s | 8m24s |
| clap-3.1.6 | 1m32s | 1m43s |
| coercions | 0m55s | 0m56s |
| cranelift-codegen-0.82.1 | 3m04s | 9m50s |
| ctfe-stress-5 | 1m12s | 1m24s |
| deeply-nested-multi | 0m33s | 2m43s |
| deep-vector | 1m25s | 1m34s |
| derive | 0m51s | 4m13s |
| diesel-1.4.8 | 2m32s | 7m15s |
| exa-0.10.1 | 2m59s | 3m00s |
| externs | 0m38s | 0m38s |
| helloworld | 0m37s | 0m37s |
| helloworld-tiny | 0m11s | 0m11s |
| html5ever-0.26.0 | 1m09s | 1m18s |
| hyper-0.14.18 | 2m10s | 2m11s |
| image-0.24.1 | 2m02s | 2m00s |
| issue-46449 | 1m16s | 1m15s |
| issue-58319 | 0m33s | 0m32s |
| issue-88862 | 0m33s | 0m32s |
| libc-0.2.124 | 1m01s | 1m01s |
| many-assoc-items | 0m58s | 0m57s |
| match-stress | 0m52s | 0m51s |
| projection-caching | 0m41s | 0m41s |
| regex-1.5.5 | 2m56s | 2m58s |
| regression-31157 | 0m55s | 0m54s |
| ripgrep-13.0.0 | 2m03s | 2m04s |
| ripgrep-13.0.0-tiny | 1m05s | 1m05s |
| rustc | 7m45s | 13m12s |
| serde-1.0.136 | 1m37s | 1m33s |
| serde_derive-1.0.136 | 1m41s | 1m38s |
| stm32f4-0.14.0 | 3m50s | 3m49s |
| syn-1.0.89 | 1m26s | 1m28s |
| token-stream-stress | 0m28s | 0m28s |
| tt-muncher | 0m45s | 0m44s |
| tuple-stress | 0m58s | 0m56s |
| ucd | 1m04s | 1m03s |
| unicode-normalization-0.1.19 | 0m52s | 0m51s |
| unify-linearly | 0m39s | 0m38s |
| unused-warnings | 1m00s | 1m01s |
| webrender-2022 | 3m46s | 3m46s |
| wf-projection-stress-65510 | 0m31s | 0m31s |
| wg-grammar | 0m54s | 0m54s |
Quite sus number diff, while nothing interesting can be seen in perf results.
Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
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- Open a pull request that references the issue number.
Research direction
Start with the status.html and compare.html pages, using the two linked performance runs as reproduction cases. Compare the displayed took/expected values with the linked perf results and trace where the differing values originate. Done means the status page no longer shows unexplained differences when the perf results are unchanged.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100