5 ms·

If it is a project you’ve recently built, it shouldn’t matter what’s in your cargo file, since none of that will change from build to build. I wonder what’s bro

If it is a project you’ve recently built, it shouldn’t matter what’s in your cargo file, since none of that will change from build to build. I wonder what’s broken. How long does it take to build a new empty project? One think that’s helped me stay “in the flow” is switching to rust-analyzer instead of the current official RLS. Much faster, I leave format on save turned on, so `cargo check` output is usually ready in about a quarter of a second after save.

johnfn 6y ago
A new empty project compiles in under a second. However, adding dependencies will add some arbitrary number to this. Additionally, every hundred lines of code seems to add some amount of time between half a second and a whole second. I did some reading and read that generics are particularly expensive to compile, so I wonder if that accounts for the variance. I can't explain why cargo deps add time, though. I LOVE rust-analyzer. It's actually what got me to reconsider Rust after I tried a year or two ago, and it is SO good.
- steveklabnik 6y ago
  Let me put it a stronger way: if you're seeing your cargo dependencies recompile every time, it is a bug. Please file one upstream. These bugs do happen, but they are bugs.
  - johnfn 6y ago
    I don't literally see my deps compile. It's just that compile time gets slower. (I wonder if it's related to the linker?) Is that still a bug? Would be happy to report it if so.
    - steveklabnik 6y ago
      Ahh. I am less sure, but I would think that's expected, given that it has to link everything together into the final binary. You're gonna end up giving the linker more work to do, as you suspected.
    - estebank 6y ago
      If the slowless you're seeing is caused by the linker, which can very well be the case, consider using LLD as you can see significant speed improvements to the linking step. https://github.com/rust-lang/rust/issues/39915#issuecomment-618726211 https://github.com/rust-lang/rust/issues/39915#issuecomment-... https://doc.rust-lang.org/1.22.0/unstable-book/compiler-flags/linker-flavor.html https://doc.rust-lang.org/1.22.0/unstable-book/compiler-flag... If installed, you can run RUSTFLAGS="-Clink-arg=-fuse-ld=lld" cargo build --release
      - johnfn 6y ago
        Looked into this :) unfortunately I run Mac so there's nothing I can do here. Tempted to dual boot Ubuntu, though.
        estebank 6y ago
        It's a shame. I'm on the same boat and not being able to use lld adds a literal minute to my builds :-/

johnfn 6y ago

A new empty project compiles in under a second. However, adding dependencies will add some arbitrary number to this. Additionally, every hundred lines of code seems to add some amount of time between half a second and a whole second. I did some reading and read that generics are particularly expensive to compile, so I wonder if that accounts for the variance. I can't explain why cargo deps add time, though. I LOVE rust-analyzer. It's actually what got me to reconsider Rust after I tried a year or two ago, and it is SO good.

steveklabnik 6y ago
Let me put it a stronger way: if you're seeing your cargo dependencies recompile every time, it is a bug. Please file one upstream. These bugs do happen, but they are bugs.
- johnfn 6y ago
  I don't literally see my deps compile. It's just that compile time gets slower. (I wonder if it's related to the linker?) Is that still a bug? Would be happy to report it if so.
  - steveklabnik 6y ago
    Ahh. I am less sure, but I would think that's expected, given that it has to link everything together into the final binary. You're gonna end up giving the linker more work to do, as you suspected.
  - estebank 6y ago
    If the slowless you're seeing is caused by the linker, which can very well be the case, consider using LLD as you can see significant speed improvements to the linking step. https://github.com/rust-lang/rust/issues/39915#issuecomment-618726211 https://github.com/rust-lang/rust/issues/39915#issuecomment-... https://doc.rust-lang.org/1.22.0/unstable-book/compiler-flags/linker-flavor.html https://doc.rust-lang.org/1.22.0/unstable-book/compiler-flag... If installed, you can run RUSTFLAGS="-Clink-arg=-fuse-ld=lld" cargo build --release
    - johnfn 6y ago
      Looked into this :) unfortunately I run Mac so there's nothing I can do here. Tempted to dual boot Ubuntu, though.
      - estebank 6y ago
        It's a shame. I'm on the same boat and not being able to use lld adds a literal minute to my builds :-/