# 2022-05-24 Triage Log

Overall a positive week for non-incremental performance (roughly 0.5% faster),
with >1% regressions on incremental benchmarks, primarily due to
[#95563](https://github.com/rust-lang/rust/pull/95563), which will hopefully be
investigated in the coming weeks.

Triage done by **@simulacrum**.
Revision range: [7355d971a954ed63293e4191f6677f60c1bc07d9..43d9f3859e0204e764161ee085a360274b5f3e9a](https://perf.rust-lang.org/?start=7355d971a954ed63293e4191f6677f60c1bc07d9&end=43d9f3859e0204e764161ee085a360274b5f3e9a&absolute=false&stat=instructions%3Au)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:-------------------------:|
| count      | 69                             | 58                               | 76                              | 52                                | 145                       |
| mean       | 1.5%                           | 2.2%                             | -1.0%                           | -3.3%                             | 0.2%                      |
| max        | 5.1%                           | 7.3%                             | -2.9%                           | -36.9%                            | 5.1%                      |

2 Regressions, 5 Improvements, 4 Mixed; 0 of them in rollups
57 artifact comparisons made in total

#### Regressions

Transition to valtrees pt1 [#97019](https://github.com/rust-lang/rust/pull/97019)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=07ae142d77f56dd48f2736605e0a6c015f2aecc6&end=cd282d7f75da9080fda0f1740a729516e7fbec68&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 4                              | 5                                | 0                               | 0                                 | 4                        |
| mean       | 1.0%                           | 0.1%                             | N/A                             | N/A                               | 1.0%                     |
| max        | 1.1%                           | 0.1%                             | N/A                             | N/A                               | 1.1%                     |

@oli-obk has suggested applying some targeted inlining as a likely resolution to
the regressions; work to follow up needs to be done. It seems like the
regression is likely to be resolved (or at least effort applied to do so).

Make write/print macros eagerly drop temporaries [#96455](https://github.com/rust-lang/rust/pull/96455)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=d12557407c7c34f1599cfba79666954291810859&end=c186f7c07912064c352f12d8b0aa9d5e5975450e&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 3                              | 0                                | 0                               | 0                                 | 3                        |
| mean       | 0.4%                           | N/A                              | N/A                             | N/A                               | 0.4%                     |
| max        | 0.6%                           | N/A                              | N/A                             | N/A                               | 0.6%                     |

Change is relatively minor and limited to just a single benchmark, so marking
the regression as triaged; further investigation is not warranted at this time.

#### Improvements

Add PID to PGO profile data filename [#97110](https://github.com/rust-lang/rust/pull/97110)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=a084b7ad35adb508bd2e053fc2a1b9a53df9536c&end=e5732a21711e7cefa6eb22e1790406b269d6197a&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 0                              | 0                                | 94                              | 54                                | 94                       |
| mean       | N/A                            | N/A                              | -0.3%                           | -0.4%                             | -0.3%                    |
| max        | N/A                            | N/A                              | -0.5%                           | -1.2%                             | -0.5%                    |

An expected improvement in our PGO scripts, with a small magnitude effect across
many benchmarks.

--remap-path-prefix: Fix duplicated path components in debuginfo [#96867](https://github.com/rust-lang/rust/pull/96867)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=e5732a21711e7cefa6eb22e1790406b269d6197a&end=936eba3b348e65b658b60218cc9237f02abdbeb4&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 0                              | 0                                | 2                               | 6                                 | 2                        |
| mean       | N/A                            | N/A                              | -0.4%                           | -4.1%                             | -0.4%                    |
| max        | N/A                            | N/A                              | -0.4%                           | -4.7%                             | -0.4%                    |

Improvements likely to be primarily driven by reducing the amount of codegen due
to simpler/smaller debuginfo.


rustdoc: Reduce clean::Type size [#93963](https://github.com/rust-lang/rust/pull/93963)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=4f372b14dea58cbff1dd76bb651f9c035d3f6e7b&end=5f33adce1bfe01e4c0c8754400bf782a95af88c9&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 0                              | 0                                | 12                              | 20                                | 12                       |
| mean       | N/A                            | N/A                              | -0.4%                           | -0.6%                             | -0.4%                    |
| max        | N/A                            | N/A                              | -0.8%                           | -0.8%                             | -0.8%                    |


rustc_parse: Move AST -> TokenStream conversion logic to rustc_ast [#97251](https://github.com/rust-lang/rust/pull/97251)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=653463731a7f01f519cf85f444869def27f00395&end=4bb4dc4672b4d80509db4c0572ae8ceeaf7d4a1c&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 0                              | 0                                | 6                               | 7                                 | 6                        |
| mean       | N/A                            | N/A                              | -0.3%                           | -0.5%                             | -0.3%                    |
| max        | N/A                            | N/A                              | -0.4%                           | -0.6%                             | -0.4%                    |


Refactor call terminator to always include destination place [#96098](https://github.com/rust-lang/rust/pull/96098)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=acb5c16fa8acf7fd3b48fc218881f006577bab1a&end=43d9f3859e0204e764161ee085a360274b5f3e9a&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 0                              | 0                                | 5                               | 17                                | 5                        |
| mean       | N/A                            | N/A                              | -0.3%                           | -0.5%                             | -0.3%                    |
| max        | N/A                            | N/A                              | -0.4%                           | -1.1%                             | -0.4%                    |


#### Mixed

Add a query for checking whether a function is an intrinsic. [#97012](https://github.com/rust-lang/rust/pull/97012)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=7355d971a954ed63293e4191f6677f60c1bc07d9&end=735efc0c703812343a5e5d19b600dac73b8a89f0&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 7                              | 9                                | 16                              | 2                                 | 23                       |
| mean       | 0.3%                           | 0.3%                             | -0.3%                           | -0.5%                             | -0.1%                    |
| max        | 0.3%                           | 0.4%                             | -0.5%                           | -0.5%                             | -0.5%                    |

Mixed results, but overall looks to be pretty neutral. The preparation for
future maintainability outweighs the possible small cost to keeping this change.
Regression was already marked as triaged by @oli-obk (thank you!).

Cache more queries on disk [#95418](https://github.com/rust-lang/rust/pull/95418)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=536020c5f97883aa9f2a90897a5adb520486d2e1&end=e6a4afc3af2d2a53f91fc8a77bdfe94bea375b29&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 33                             | 32                               | 65                              | 28                                | 98                       |
| mean       | 0.8%                           | 1.6%                             | -1.0%                           | -4.4%                             | -0.4%                    |
| max        | 2.1%                           | 4.0%                             | -3.6%                           | -33.0%                            | -3.6%                    |

This is overall an improvement, with regressions primarily limited to secondary
benchmarks. Mixed results are fairly expected from a change like this; marking
the regression as triaged. @cjgillot (PR author) also posted a good summary:

> This PR caches many more queries' results on disk. The queries have been
> chosen to be: (1) outputs of typechecking, and (2) parts of metadata. This
> caching allows for wide and large compile time savings, up to 36%. The
> tradeoff is a compile time increase (4%) when these caches cannot be usefully
> used, and a increased on-disk size around 30%.

Move the extended lifetime resolution into typeck context [#95563](https://github.com/rust-lang/rust/pull/95563)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=acfd327fd4e3a302ebb0a077f422a527a7935333&end=653463731a7f01f519cf85f444869def27f00395&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 97                             | 42                               | 42                              | 34                                | 139                      |
| mean       | 1.8%                           | 3.0%                             | -0.6%                           | -0.5%                             | 1.1%                     |
| max        | 5.8%                           | 8.9%                             | -1.9%                           | -1.4%                             | 5.8%                     |

Looks like a fairly large regression across a number of benchmarks, though
limited to the incremental scenarios. Non-incremental benchmarks show an
improvement (hence the mixed results). Left a
[comment](https://github.com/rust-lang/rust/pull/95563#issuecomment-1135994637)
on the PR asking for clarification and further investigation.

Update `rustc` PGO benchmark list [#97120](https://github.com/rust-lang/rust/pull/97120)
[(Comparison Link)](https://perf.rust-lang.org/compare.html?start=222c5724ecc922fe67815f428c19f82c129d9386&end=ee160f2f5e73b6f5954bc33f059c316d9e8582c4&stat=instructions:u)

|            | Regressions 😿 <br />(primary) | Regressions 😿 <br />(secondary) | Improvements 🎉 <br />(primary) | Improvements 🎉 <br />(secondary) | All 😿 🎉 <br />(primary) |
|:----------:|:------------------------------:|:--------------------------------:|:-------------------------------:|:---------------------------------:|:------------------------:|
| count      | 3                              | 18                               | 83                              | 53                                | 86                       |
| mean       | 0.3%                           | 0.8%                             | -0.5%                           | -0.5%                             | -0.5%                    |
| max        | 0.4%                           | 1.8%                             | -1.3%                           | -1.1%                             | -1.3%                    |

Overall an improvement, some slight regressions are expected from a larger
change like this which bumps PGO inputs.