`removeItem` performance

👋🏼 Hi,

First of all, thanks for this amazing work.

We are using the file-system IO components at Tuist, and I'd like to bring up something that we notice regarding the performance of the NIOFileSystem.FileSystem.removeItem function.

When we run it against a large directory with many nested directories and and files, we noticed the performance is much worse than using FileManager or just rm -rf in a Linux environment. We benchmarked the performance with hyperfine and the results are below.

Looking at the implementation, it seems that we are not parallelising at all, so I was wondering if this is something intentional, or if it's ok to refactor that code to run as much as possible in parallel.

Bechmarks

With NIOFileSystem

Benchmark

Time (mean ± σ): 67.939 s ± 4.450 s [User: 61.906 s, System: 3.205 s]
Range (min … max): 63.684 s … 77.757 s 10 runs

With Foundation's FileManager

Benchmark:

Time (mean ± σ): 5.857 s ± 0.251 s [User: 1.430 s, System: 2.067 s]
Range (min … max): 5.419 s … 6.190 s 10 runs

With `rm -rf`

Benchmark: Time (mean ± σ): 3.150 s ± 0.386 s [User: 0.022 s, System: 1.666 s] Range (min … max): 2.225 s … 3.585 s 10 runs

apple / swift-nio