Tracking issue for stabilizing "pipelined compilation" #60988

alexcrichton · 2019-05-20T22:07:15Z

This issue is intended to be an overall tracking issue for stabilizing the recently implemented feature of "pipelined compilation". This tracking issue spans both Cargo and rustc, as support currently lives in both. It also builds on top of a number of other tracking issues, since they're unstable features used to implement pipelined compilation!

For a bit of background, pipelined compilation has an initial set of notes about its implementation and initially had these tracking issues:

Currently today everything is implemented and available in nightly rustc. There is a thread on internals which is tasked with gaining user experience about pipelining and see the performance impact. A collation of these measurements is quite promising and I feel personally is convincing enough to push on stabilizing all the sub-features!

Known blockers for stabilization:

-Z emit-artifact-notifications - this is how Cargo learns the moment metadata is ready.
--json-rendered - this is how Cargo continues to provide pretty error messages.
There is no way to combine --message-format=short in Cargo with pipelining. The compiler currently has --error-format=json|short|human, but for this feature in Cargo we'll need something like --error-format=short-json or something like that. Basically some way to request that the rendered field in the JSON diagnostic is a "short message", not the long one.
Cargo pipelining is known to break with sccache, this should be investigated and fixed one way or another. (fixed in Cache rmeta files whenever metadata is present in emit. mozilla/sccache#441)
Pipelining fails with the RLS due to multiple --error-format flags (fixed in Update RLS #62176)

Possible future work:

Should we game out what a "fully pipelined" story might look like? What if rustc blocked waiting for Cargo to tell it to proceed into the linking phase?

The text was updated successfully, but these errors were encountered:

Centril · 2019-05-21T01:08:24Z

Reading the various issues and PRs, I got the impression that metadata is generated at earliest post static analysis, is that correct?

nnethercote · 2019-05-21T01:39:10Z

Yes: metadata is now generated right at the start of code generation, immediately after all the checking (typeck, borrowck, etc.) finish. This is the best place for the initial pipelining implementation.

One might argue that metadata generation should be moved earlier. That would help with successful builds, but slow down builds that trigger compile errors. Given that a lot of Rust compiler invocations end in compile errors during the normal development cycle, slowing down such invocations would be bad.

Another possibility is to generate metadata in parallel with checking. That might give the best of both worlds. But that's a bigger change.

Centril · 2019-05-21T01:52:23Z

One might argue that metadata generation should be moved earlier.

No no... ;) At the start of code-gen sounds good to me and we should be cautious with moving it too much earlier as that can mess with language design.

oli-obk · 2019-05-21T11:26:38Z

There is no way to combine --message-format=short in Cargo with pipelining

This is trivial to implement with --json-rendered. I can mentor this in #60987

jsgf · 2019-05-21T16:42:11Z

It might be useful to have multiple rendered forms in the json output.

@alexcrichton

…hton Make -Zemit-artifact-notifications also emit the artifact type This is easier for tooling to handle than trying to reverse-engineer the type from the filename extension. The field name and value is intended to reflect the `--emit` command-line option. Related issues rust-lang#60988 rust-lang#58465 cc @alexcrichton

@alexcrichton

…hton Make -Zemit-artifact-notifications also emit the artifact type This is easier for tooling to handle than trying to reverse-engineer the type from the filename extension. The field name and value is intended to reflect the `--emit` command-line option. Related issues rust-lang#60988 rust-lang#58465 cc @alexcrichton

alexcrichton · 2019-06-14T19:08:33Z

I've proposed stabilization of --json-rendered as well as -Z emit-artifact-notifications which, if stabilized, can allow Cargo to switch over to using these by default and stabilizing pipelined compilation.

jsgf · 2019-06-17T20:24:31Z

I'd like to make sure there's a stable way to make sure that --emit metadata on its own produces metadata suitable as an input to a next build stage. I'm fine with the plain cargo check metadata being incomplete if that allows it to be emitted a little faster, but I'd like to have the option of two-invocation pipelining without paying the cost of --emit metadata,link.

Context:

Invoking rustc twice is going to be easier to implement in Buck than full pipelining initially
Full pipelining is the goal, but Buck is not currently set up for it (I believe Bazel is in a similar position)
The extra CPU overhead of two rustc invocations is fine if it helps shorten the build critical path
But the cost of two complete builds is too much

(cc @bolinfest)

alexcrichton · 2019-06-18T17:32:44Z

I agree that it should be the case, but that seems like a separable stabilization issue from this which is enabling Cargo's internal pipelined compilation.

Xanewok · 2019-06-24T12:26:15Z

@alexcrichton IIUC it seems that pipelining always emits --error-format which currently seems to break the RLS due to error: Option 'error-format' given more than once (rust-lang/rls#1484).

The immediate fix is to filter the injected --error-format flag ourselves and continue with our --error-format=json flag (will that break the pipelining?). However, I imagine it'd be better to allow multiple occurrences of these with the later ones taking precedence not to reimplement command arguments parsing and filtering in rustc wrappers. Does that sound like a good idea?

alexcrichton · 2019-06-25T06:22:35Z

@Xanewok that sounds reasonable to me yeah with the last option taking precedence!

@alexcrichton

Update RLS Merged PRs: * fix(cmd): make clear_env_rust_log default to false (rust-lang/rls#1486) - Retain `RUST_LOG` in `rls --cli` mode * Pass --file-lines to rustfmt only if specified (rust-lang/rls#1497) - Fix entire-file formatting when using external rustfmt (specified via `rustfmt_path` config) * Ensure that --error-format is only passed once to `rustc` (rust-lang/rls#1500) - Unbreaks RLS when used together with Cargo [pipelining build](rust-lang#60988) feature (@alexcrichton I'd consider this a stabilization blocker, mind adding it to the tracking issue for the record? 🙇‍♂️ )

@alexcrichton

Update RLS Merged PRs: * fix(cmd): make clear_env_rust_log default to false (rust-lang/rls#1486) - Retain `RUST_LOG` in `rls --cli` mode * Pass --file-lines to rustfmt only if specified (rust-lang/rls#1497) - Fix entire-file formatting when using external rustfmt (specified via `rustfmt_path` config) * Ensure that --error-format is only passed once to `rustc` (rust-lang/rls#1500) - Unbreaks RLS when used together with Cargo [pipelining build](rust-lang#60988) feature (@alexcrichton I'd consider this a stabilization blocker, mind adding it to the tracking issue for the record? 🙇‍♂️ )

@alexcrichton

Update RLS Merged PRs: * fix(cmd): make clear_env_rust_log default to false (rust-lang/rls#1486) - Retain `RUST_LOG` in `rls --cli` mode * Pass --file-lines to rustfmt only if specified (rust-lang/rls#1497) - Fix entire-file formatting when using external rustfmt (specified via `rustfmt_path` config) * Ensure that --error-format is only passed once to `rustc` (rust-lang/rls#1500) - Unbreaks RLS when used together with Cargo [pipelining build](rust-lang#60988) feature (@alexcrichton I'd consider this a stabilization blocker, mind adding it to the tracking issue for the record? 🙇‍♂️ )

alexcrichton · 2019-07-17T21:16:25Z

The two blocking issues are now in FCP:

and I have posted two PRs to stabilize the implementation:

This commit stabilizes options in the compiler necessary for Cargo to enable "pipelined compilation" by default. The concept of pipelined compilation, how it's implemented, and what it means for rustc are documented in rust-lang#60988. This PR is coupled with a PR against Cargo (rust-lang/cargo#7143) which updates Cargo's support for pipelined compliation to rustc, and also enables support by default in Cargo. (note that the Cargo PR cannot land until this one against rustc lands). The technical changes performed here were to stabilize the functionality proposed in rust-lang#60419 and rust-lang#60987, the underlying pieces to enable pipelined compilation support in Cargo. The issues have had some discussion during stabilization, but the newly stabilized surface area here is: * A new `--json` flag was added to the compiler. * The `--json` flag can be passed multiple times. * The value of the `--json` flag is a comma-separated list of directives. * The `--json` flag cannot be combined with `--color` * The `--json` flag must be combined with `--error-format=json` * The acceptable list of directives to `--json` are: * `diagnostic-short` - the `rendered` field of diagnostics will have a "short" rendering matching `--error-format=short` * `diagnostic-rendered-ansi` - the `rendered` field of diagnostics will be colorized with ansi color codes embedded in the string field * `artifacts` - JSON blobs will be emitted for artifacts being emitted by the compiler The unstable `-Z emit-artifact-notifications` and `--json-rendered` flags have also been removed during this commit as well. Closes rust-lang#60419 Closes rust-lang#60987 Closes rust-lang#60988

…r=oli-obk rustc: Stabilize options for pipelined compilation This commit stabilizes options in the compiler necessary for Cargo to enable "pipelined compilation" by default. The concept of pipelined compilation, how it's implemented, and what it means for rustc are documented in #60988. This PR is coupled with a PR against Cargo (rust-lang/cargo#7143) which updates Cargo's support for pipelined compliation to rustc, and also enables support by default in Cargo. (note that the Cargo PR cannot land until this one against rustc lands). The technical changes performed here were to stabilize the functionality proposed in #60419 and #60987, the underlying pieces to enable pipelined compilation support in Cargo. The issues have had some discussion during stabilization, but the newly stabilized surface area here is: * A new `--json` flag was added to the compiler. * The `--json` flag can be passed multiple times. * The value of the `--json` flag is a comma-separated list of directives. * The `--json` flag cannot be combined with `--color` * The `--json` flag must be combined with `--error-format=json` * The acceptable list of directives to `--json` are: * `diagnostic-short` - the `rendered` field of diagnostics will have a "short" rendering matching `--error-format=short` * `diagnostic-rendered-ansi` - the `rendered` field of diagnostics will be colorized with ansi color codes embedded in the string field * `artifacts` - JSON blobs will be emitted for artifacts being emitted by the compiler The unstable `-Z emit-artifact-notifications` and `--json-rendered` flags have also been removed during this commit as well. Closes #60419 Closes #60987 Closes #60988

umanwizard · 2019-08-09T03:14:18Z

The NOTES.md link in the description is dead.

alexcrichton mentioned this issue May 20, 2019

Implement "pipelined" rustc compilation (compiler side) #58465

Closed

jsgf mentioned this issue May 21, 2019

Make -Zemit-artifact-notifications also emit the artifact type #61014

Merged

alexcrichton mentioned this issue Jun 14, 2019

Tracking issue for unstable --json-rendered flag #60987

Closed

3 tasks

This was referenced Jun 25, 2019

Accept multiple --error-format flags #62134

Closed

Update RLS #62176

Merged

alexcrichton mentioned this issue Jul 17, 2019

rustc: Stabilize options for pipelined compilation #62766

Merged

bors closed this as completed in #62766 Jul 30, 2019

est31 mentioned this issue Dec 20, 2019

Support generating interface files separately (and before) compiled code #39541

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nnethercote mentioned this issue Mar 2, 2023

Compiler Performance Tracking Issue #48547

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Tracking issue for stabilizing "pipelined compilation" #60988

Tracking issue for stabilizing "pipelined compilation" #60988

alexcrichton commented May 20, 2019 •

edited by tmandry

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Centril commented May 21, 2019

nnethercote commented May 21, 2019

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oli-obk commented May 21, 2019

jsgf commented May 21, 2019

alexcrichton commented Jun 14, 2019

jsgf commented Jun 17, 2019

alexcrichton commented Jun 18, 2019

Xanewok commented Jun 24, 2019

alexcrichton commented Jun 25, 2019

alexcrichton commented Jul 17, 2019

umanwizard commented Aug 9, 2019

Tracking issue for stabilizing "pipelined compilation" #60988

Tracking issue for stabilizing "pipelined compilation" #60988

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alexcrichton commented May 20, 2019 • edited by tmandry Loading

Centril commented May 21, 2019

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umanwizard commented Aug 9, 2019

alexcrichton commented May 20, 2019 •

edited by tmandry

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