pretty much the only place where it's meaningfully slower is the allocator (which has a massive impact) so in chimera we have a special musl build that uses llvm's scudo instead (same as e.g. android) and is faster as well as more secure than glibc's allocator

the rest is mostly fewer specialized implementations of stuff for different cpus, but that rarely makes a difference in practice (i.e. outside of microbenchmarks)

the overall standards compliance is pretty good in musl