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Compile some CGUs in parallel at the start of codegen #67889

Merged
merged 2 commits into from
Jan 11, 2020
Merged

Compile some CGUs in parallel at the start of codegen #67889

merged 2 commits into from
Jan 11, 2020

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Zoxc
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@Zoxc Zoxc commented Jan 5, 2020

This brings the compilation time for syntex_syntax from 11.542s to 10.453s with 6 threads in non-incremental debug mode. Just compiling n CGUs in parallel at the beginning of codegen seems sufficient to get rid of the staircase effect, at least for syntex_syntax.

Based on #67777.

r? @michaelwoerister
cc @alexcrichton @Mark-Simulacrum

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 5, 2020
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michaelwoerister reviewed Jan 6, 2020
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Looks good to me with nits addressed.

I hope we really can get rid of OnGoingCodegen entirely at some point.

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Heads up, @bjorn3: This PR changes the codegen backend protocol.

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bjorn3 commented Jan 6, 2020

Thanks for the ping @michaelwoerister! This is in a part which I don't yet use though. Because cranelift-module compiles a function as soon as you define it, isn't possible for me to use multiple threads until there are parallel rustc builds for every nightly.

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bors commented Jan 6, 2020

☔ The latest upstream changes (presumably #67886) made this pull request unmergeable. Please resolve the merge conflicts.

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This looks like a nice small improvement!

In the limit I'm looking forward to when we can fully reap the benefits here, including:

  • Removal of the coordinator thread for LLVM CGU management
  • Removal of cost approximation to know when to CGU and when to optimize
  • Straight-line code to express "codegen and optimize everything" all in one function that's much easier to read than the coordinator thread

I don't think we can get here until we remove the single-threaded compiler completely though. While this is adding complexity to an already complex backend it's not too too bad and has some modest wins. I think the biggest wins though are going to come when we're able to remove the coordinator thread entirely.

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Thanks, @Zoxc.

@bors r+

I'm r+ing under the assumption that the job server questions is resolved to @Mark-Simulacrum's and @alexcrichton's satisfaction. I don't know the details there.

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bors commented Jan 9, 2020

📌 Commit e3a36c0d78c69ea59a6bde4bae0729dc3545a7b4 has been approved by michaelwoerister

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 9, 2020
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bors commented Jan 9, 2020

☔ The latest upstream changes (presumably #67988) made this pull request unmergeable. Please resolve the merge conflicts.

@bors bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jan 9, 2020
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Zoxc commented Jan 9, 2020

@bors r=michaelwoerister

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bors commented Jan 9, 2020

📌 Commit 69bacd0 has been approved by michaelwoerister

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jan 9, 2020
Centril added a commit to Centril/rust that referenced this pull request Jan 11, 2020
@Centril
Rollup merge of rust-lang#67889 - Zoxc:parallel-cgus, r=michaelwoerister
2f0527c 
Compile some CGUs in parallel at the start of codegen

This brings the compilation time for `syntex_syntax` from 11.542s to 10.453s with 6 threads in non-incremental debug mode. Just compiling `n` CGUs in parallel at the beginning of codegen seems sufficient to get rid of the staircase effect, at least for `syntex_syntax`.

Based on rust-lang#67777.

r? @michaelwoerister
cc @alexcrichton @Mark-Simulacrum
@Centril Centril mentioned this pull request Jan 11, 2020
Closed
Centril added a commit to Centril/rust that referenced this pull request Jan 11, 2020
@Centril
Rollup merge of rust-lang#67889 - Zoxc:parallel-cgus, r=michaelwoerister
72bf6f4 
Compile some CGUs in parallel at the start of codegen

This brings the compilation time for `syntex_syntax` from 11.542s to 10.453s with 6 threads in non-incremental debug mode. Just compiling `n` CGUs in parallel at the beginning of codegen seems sufficient to get rid of the staircase effect, at least for `syntex_syntax`.

Based on rust-lang#67777.

r? @michaelwoerister
cc @alexcrichton @Mark-Simulacrum
@Centril Centril mentioned this pull request Jan 11, 2020
Closed
bors added a commit that referenced this pull request Jan 11, 2020
@bors
Auto merge of #68124 - Centril:rollup-4h2ybcj, r=Centril
13ad02f 
Rollup of 9 pull requests

Successful merges:

 - #67000 (Promote references to constants instead of statics)
 - #67756 (Collector tweaks)
 - #67889 (Compile some CGUs in parallel at the start of codegen)
 - #67930 (Rename Result::as_deref_ok to as_deref)
 - #68018 (feature_gate: Remove `GateStrength`)
 - #68070 (clean up E0185 explanation)
 - #68072 (Fix ICE #68058)
 - #68114 (Don't require `allow_internal_unstable` unless `staged_api` is enabled.)
 - #68120 (Ban `...X` pats, harden tests, and improve diagnostics)

Failed merges:

r? @ghost
Centril added a commit to Centril/rust that referenced this pull request Jan 11, 2020
@Centril
Rollup merge of rust-lang#67889 - Zoxc:parallel-cgus, r=michaelwoerister
7b741fb 
Compile some CGUs in parallel at the start of codegen

This brings the compilation time for `syntex_syntax` from 11.542s to 10.453s with 6 threads in non-incremental debug mode. Just compiling `n` CGUs in parallel at the beginning of codegen seems sufficient to get rid of the staircase effect, at least for `syntex_syntax`.

Based on rust-lang#67777.

r? @michaelwoerister
cc @alexcrichton @Mark-Simulacrum
@Centril Centril mentioned this pull request Jan 11, 2020
Merged
bors added a commit that referenced this pull request Jan 11, 2020
@bors
Auto merge of #68126 - Centril:rollup-cz5u7xx, r=Centril
bfd0487 
Rollup of 8 pull requests

Successful merges:

 - #67756 (Collector tweaks)
 - #67889 (Compile some CGUs in parallel at the start of codegen)
 - #67930 (Rename Result::as_deref_ok to as_deref)
 - #68018 (feature_gate: Remove `GateStrength`)
 - #68070 (clean up E0185 explanation)
 - #68072 (Fix ICE #68058)
 - #68114 (Don't require `allow_internal_unstable` unless `staged_api` is enabled.)
 - #68120 (Ban `...X` pats, harden tests, and improve diagnostics)

Failed merges:

r? @ghost
@bors bors merged commit 69bacd0 into rust-lang:master Jan 11, 2020
@Zoxc Zoxc deleted the parallel-cgus branch January 11, 2020 19:11
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