rust-analyzer is slow to compile

[matklad]

Both ra_hir and ra_ide_api are really slow to compiler, which makes fix & test loop rather frustrating. Note that tests are extremely fast themselves, it's compile time that hurts us badly.

We need to do something with it...

[lnicola]

Codegen seems to be taking an awful lot of time...

With debug=0:

But overall that's just a tiny improvement.

[kjeremy]

At the moment we carry around 2 versions of winapi which adds over 30 seconds to my build. I can get it down to (I think) one version of 0.2.8 being held back by mio.

[kjeremy]

@inicola is that cargo timings with build? 88s to generate metadata on ra_hir?

[lnicola]

Yeah, and 102s by default. Maybe there's a lot of generic code?

[matklad]

Hm, that reminds me that we should set debug = 1 for the dev profile, to save some disk space...

[lnicola]

Another interesting thing is that I tried to use lld. Even though it helped quite a lot on other projects, it seems to make no difference here.

[lnicola]

Some random -Z self-profile measurements, which don't tell us anything new:

ra_hir:

+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| Item                                          | Self time | % of total time | Item count | Cache hits | Blocked time | Incremental load time |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_module_optimize_module_passes            | 129.32s   | 35.794          | 199        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_thin_lto_optimize                        | 75.69s    | 20.950          | 199        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_module_codegen_emit_obj                  | 55.74s    | 15.429          | 199        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| codegen_crate                                 | 36.53s    | 10.111          | 1          | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| codegen_module                                | 16.45s    | 4.553           | 199        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_thin_lto_import                          | 13.98s    | 3.869           | 199        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_module_optimize_function_passes          | 6.76s     | 1.870           | 199        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| typeck_tables_of                              | 3.29s     | 0.910           | 2798       | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_module_codegen_make_bitcode              | 2.61s     | 0.723           | 199        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| evaluate_obligation                           | 1.35s     | 0.374           | 79783      | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| monomorphization_collector_graph_walk         | 1.04s     | 0.289           | 1          | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+

ra_ide_api:

+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| Item                                          | Self time | % of total time | Item count | Cache hits | Blocked time | Incremental load time |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_module_optimize_module_passes            | 166.80s   | 35.059          | 305        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_thin_lto_optimize                        | 96.95s    | 20.377          | 305        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_module_codegen_emit_obj                  | 69.66s    | 14.642          | 305        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| codegen_crate                                 | 50.28s    | 10.568          | 1          | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_thin_lto_import                          | 26.33s    | 5.533           | 305        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| codegen_module                                | 25.05s    | 5.266           | 305        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_module_optimize_function_passes          | 10.47s    | 2.200           | 305        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| LLVM_module_codegen_make_bitcode              | 3.14s     | 0.660           | 305        | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| normalize_projection_ty                       | 1.84s     | 0.386           | 15240      | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| monomorphization_collector_graph_walk         | 1.74s     | 0.367           | 1          | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| evaluate_obligation                           | 1.46s     | 0.307           | 74165      | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+
| codegen_fulfill_obligation                    | 1.46s     | 0.307           | 23807      | 0          | 0.00ns       | 0.00ns                |
+-----------------------------------------------+-----------+-----------------+------------+------------+--------------+-----------------------+

[lnicola]

chrome_profiler.zip

[ice1000]

Will further modularization help?

[kjeremy]

Might be relevant for cargo test rust-lang/cargo#7514

[matklad]

On thing that helps a bit is using lld:

λ cat ~/.cargo/config 
[build]
rustflags = [ "-C", "link-arg=-fuse-ld=lld" ]⏎

[lnicola]

That's strange, I tried it a couple of times, and it made zero difference for RA. It does help a lot on other projects.