Decouple serde from its derive crate
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By not activating the `derive` feature on `serde`, the compilation speed can be improved by a lot. This is because `serde` can then compile in parallel to `serde_derive`, allowing it to finish compilation possibly even before `serde_derive`, unblocking all the crates waiting for `serde` to start compiling much sooner. As it turns out the main deciding factor for how long the compile time of a project is, is primarly determined by the depth of dependencies rather than the width. In other words, a crate's compile times aren't affected by how many crates it depends on, but rather by the longest chain of dependencies that it needs to wait on. In many cases `serde` is part of that long chain, as it is part of a long chain if the `derive` feature is active: `proc-macro2` compile build script > `proc-macro2` run build script > `proc-macro2` > `quote` > `syn` > `serde_derive` > `serde` > `serde_json` (or any crate that depends on serde) By decoupling it from `serde_derive`, the chain is shortened and compile times get much better. Check this issue for a deeper elaboration: serde-rs/serde#2584 For `wasmtime` I'm seeing a reduction from 24.75s to 22.45s when compiling in `release` mode. This is because wasmtime through `gimli` has a dependency on `indexmap` which can only start compiling when `serde` is finished, which you want to happen as early as possible so some of wasmtime's dependencies can start compiling. To measure the full effect, the dependencies can't by themselves activate the `derive` feature. I've upstreamed a patch for `fxprof-processed-profile` which was the only dependency that activated it for `wasmtime` (not yet published to crates.io). `wasmtime-cli` and co. may need patches for their dependencies to see a similar improvement.
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eduardomourar
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By not activating the `derive` feature on `serde`, the compilation speed can be improved by a lot. This is because `serde` can then compile in parallel to `serde_derive`, allowing it to finish compilation possibly even before `serde_derive`, unblocking all the crates waiting for `serde` to start compiling much sooner. As it turns out the main deciding factor for how long the compile time of a project is, is primarly determined by the depth of dependencies rather than the width. In other words, a crate's compile times aren't affected by how many crates it depends on, but rather by the longest chain of dependencies that it needs to wait on. In many cases `serde` is part of that long chain, as it is part of a long chain if the `derive` feature is active: `proc-macro2` compile build script > `proc-macro2` run build script > `proc-macro2` > `quote` > `syn` > `serde_derive` > `serde` > `serde_json` (or any crate that depends on serde) By decoupling it from `serde_derive`, the chain is shortened and compile times get much better. Check this issue for a deeper elaboration: serde-rs/serde#2584 For `wasmtime` I'm seeing a reduction from 24.75s to 22.45s when compiling in `release` mode. This is because wasmtime through `gimli` has a dependency on `indexmap` which can only start compiling when `serde` is finished, which you want to happen as early as possible so some of wasmtime's dependencies can start compiling. To measure the full effect, the dependencies can't by themselves activate the `derive` feature. I've upstreamed a patch for `fxprof-processed-profile` which was the only dependency that activated it for `wasmtime` (not yet published to crates.io). `wasmtime-cli` and co. may need patches for their dependencies to see a similar improvement.
alexcrichton
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I noticed recently that `wit-component` was relatively slow to compile and it's going to be an introductory requirement for any Rust crates so I wanted to optimize its build a little bit. This is the first optimization which is to disable the `derive` feature of the `serde` crate to enable build build pipelining opportunities. This is the same as bytecodealliance/wasmtime#6917
alexcrichton
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* Use `serde_derive` instead of the `derive` feature I noticed recently that `wit-component` was relatively slow to compile and it's going to be an introductory requirement for any Rust crates so I wanted to optimize its build a little bit. This is the first optimization which is to disable the `derive` feature of the `serde` crate to enable build build pipelining opportunities. This is the same as bytecodealliance/wasmtime#6917 * Fix build issue
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By not activating the
derivefeature onserde, the compilation speed can be improved by a lot. This is becauseserdecan then compile in parallel toserde_derive, allowing it to finish compilation possibly even beforeserde_derive, unblocking all the crates waiting forserdeto start compiling much sooner.As it turns out the main deciding factor for how long the compile time of a project is, is primarly determined by the depth of dependencies rather than the width. In other words, a crate's compile times aren't affected by how many crates it depends on, but rather by the longest chain of dependencies that it needs to wait on. In many cases
serdeis part of that long chain, as it is part of a long chain if thederivefeature is active:proc-macro2compile build script >proc-macro2run build script >proc-macro2>quote>syn>serde_derive>serde>serde_json(or any crate that depends on serde)By decoupling it from
serde_derive, the chain is shortened and compile times get much better.Check this issue for a deeper elaboration:
serde-rs/serde#2584
For
wasmtimeI'm seeing a reduction from 24.75s to 22.45s when compiling inreleasemode. This is because wasmtime throughgimlihas a dependency onindexmapwhich can only start compiling whenserdeis finished, which you want to happen as early as possible so some of wasmtime's dependencies can start compiling.To measure the full effect, the dependencies can't by themselves activate the
derivefeature. I've upstreamed a patch forfxprof-processed-profilewhich was the only dependency that activated it forwasmtime(not yet published to crates.io).wasmtime-cliand co. may need patches for their dependencies to see a similar improvement.