Use a new no_force query modifier for check_representability#153996
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Zalathar wants to merge 2 commits intorust-lang:mainfrom
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Use a new no_force query modifier for check_representability#153996Zalathar wants to merge 2 commits intorust-lang:mainfrom
no_force query modifier for check_representability#153996Zalathar wants to merge 2 commits intorust-lang:mainfrom
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@bors try @rust-timer queue |
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Use a new `no_force` query modifier for `check_representability`
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Finished benchmarking commit (76ac687): comparison URL. Overall result: ✅ improvements - no action neededBenchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf. @bors rollup=never Instruction countOur most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.
Max RSS (memory usage)Results (primary -1.5%)A less reliable metric. May be of interest, but not used to determine the overall result above.
CyclesThis benchmark run did not return any relevant results for this metric. Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 481.948s -> 480.072s (-0.39%) |
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Remove the `anon` query modifier Prior experiments: - #152268 - #153996 [Zulip thread: *Removing the `anon` query modifier*](https://rust-lang.zulipchat.com/#narrow/channel/582699-t-compiler.2Fquery-system/topic/Removing.20the.20.60anon.60.20query.20modifier/with/580760962) --- There are currently three queries that use the `anon` modifier: - `check_representability` - `check_representability_adt_ty` - `erase_and_anonymize_regions_ty` It seems that none of them are using `anon` in an essential way. According to comments and tests, the *representability* queries mainly care about not being eligible for forcing (despite having a recoverable key type), so that if a cycle does occur then the entire cycle will be on the query stack. Replacing `anon` with a new `no_force` modifier gives a modest perf improvement. The `erase_and_anonymize_regions_ty` query appears to be using `anon` to reduce the dep-graph overhead of a query that is expected to not call any other queries (and thus have no dependencies). Replacing `anon` with either `no_hash` or nothing appears to give only a very small perf hit on `cargo` benchmarks, which is justified by the fact that it lets us remove a lot of machinery for anonymous queries. We still need to retain some of the machinery for anonymous *tasks*, because the non-query task `DepKind::TraitSelect` still uses it. --- I have some ideas for a follow-up that will reduce dep-graph overhead by replacing *all* zero-dependency nodes with a singleton node, but I want to keep that separate in case it causes unexpected issues and needs to be bisected or reverted.
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Remove the `anon` query modifier Prior experiments: - #152268 - #153996 [Zulip thread: *Removing the `anon` query modifier*](https://rust-lang.zulipchat.com/#narrow/channel/582699-t-compiler.2Fquery-system/topic/Removing.20the.20.60anon.60.20query.20modifier/with/580760962) --- There are currently three queries that use the `anon` modifier: - `check_representability` - `check_representability_adt_ty` - `erase_and_anonymize_regions_ty` It seems that none of them are using `anon` in an essential way. According to comments and tests, the *representability* queries mainly care about not being eligible for forcing (despite having a recoverable key type), so that if a cycle does occur then the entire cycle will be on the query stack. Replacing `anon` with a new `no_force` modifier gives a modest perf improvement. The `erase_and_anonymize_regions_ty` query appears to be using `anon` to reduce the dep-graph overhead of a query that is expected to not call any other queries (and thus have no dependencies). Replacing `anon` with either `no_hash` or nothing appears to give only a very small perf hit on `cargo` benchmarks, which is justified by the fact that it lets us remove a lot of machinery for anonymous queries. We still need to retain some of the machinery for anonymous *tasks*, because the non-query task `DepKind::TraitSelect` still uses it. --- I have some ideas for a follow-up that will reduce dep-graph overhead by replacing *all* zero-dependency nodes with a singleton node, but I want to keep that separate in case it causes unexpected issues and needs to be bisected or reverted.
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Remove the `anon` query modifier Prior experiments: - rust-lang/rust#152268 - rust-lang/rust#153996 [Zulip thread: *Removing the `anon` query modifier*](https://rust-lang.zulipchat.com/#narrow/channel/582699-t-compiler.2Fquery-system/topic/Removing.20the.20.60anon.60.20query.20modifier/with/580760962) --- There are currently three queries that use the `anon` modifier: - `check_representability` - `check_representability_adt_ty` - `erase_and_anonymize_regions_ty` It seems that none of them are using `anon` in an essential way. According to comments and tests, the *representability* queries mainly care about not being eligible for forcing (despite having a recoverable key type), so that if a cycle does occur then the entire cycle will be on the query stack. Replacing `anon` with a new `no_force` modifier gives a modest perf improvement. The `erase_and_anonymize_regions_ty` query appears to be using `anon` to reduce the dep-graph overhead of a query that is expected to not call any other queries (and thus have no dependencies). Replacing `anon` with either `no_hash` or nothing appears to give only a very small perf hit on `cargo` benchmarks, which is justified by the fact that it lets us remove a lot of machinery for anonymous queries. We still need to retain some of the machinery for anonymous *tasks*, because the non-query task `DepKind::TraitSelect` still uses it. --- I have some ideas for a follow-up that will reduce dep-graph overhead by replacing *all* zero-dependency nodes with a singleton node, but I want to keep that separate in case it causes unexpected issues and needs to be bisected or reverted.
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This is currently very speculative; I have no idea whether it will be good for perf. But it seems nice to get rid of some
anonmodifiers if they aren't actually needed.