Add installation notes for Arch Linux users

[murlakatamenka]

Note: 2 of the AUR packages mentioned are maintained by me and are updated rather promptly.

[matklad]

bors r+

Thanks! And thanks for packaging in the first place :)

[lnicola]

Thanks for packaging it. It might be worth enabling jemalloc, see #3459 and #3531.

[murlakatamenka]

@lnicola shouldn't it be unnecessary? Currently binary is built with just cargo build --release --locked and thus uses default toolchain and system's allocator. I assume people use stable/nightly-x86_64-unknown-linux-gnu by default and use musl target just to compile a generic *nix binary that would fit everyone.

[lnicola]

Currently binary is built with just cargo build --release --locked and thus uses default toolchain and system's allocator. I assume people use stable/nightly-x86_64-unknown-linux-gnu by default

Yes, but enabling jemalloc (nb. that's a package feature, not a toolchain) makes it marginally faster (8.7% in my test) and enables memory usage reporting via a custom LSP / Code command. I don't know if that's worth the effort and build time hit, though. We don't try to ship the fastest binary anyway -- that would imply adding codegen-units = 1 and lto = on.

[murlakatamenka]

I meant that using jemalloc is more beneficial for musl target (with slower allocator) and questionable for default unkown-linux-gnu one that will be used for building on users' Arch machines (with faster glibc allocator). But now I learned that it may still make sense to use jemalloc for non-musl targets.

Thanks, I'll test the tradeoff of longer compile time / faster binary and see whether using this feature is worth it.

[matklad]

I personally run rust-analyzer compiled from source with system allocator (that's on NixOS, so glibc)