tokio::io::copy slower than std io::copy

[radumarias]

I did a file copy speed test between these 2 and seems tokio::io::copy is much slower than sync std io::copy

I noticed this while implementing my own tokio AsyncWrite.

Here are the results on my machine for a file of 894MB

filesize = 894MB
tokio write duration = 2.661018252s, speed MB/s 336.2394975276158
std write duration = 418.723487ms, speed MB/s 2136.826492286769

here is the code I used playground

I then tried tokio-uring, Indeed better but still not close to std
Tested writing 840 MB of content to a file

tokio write duration = 710.079182ms, speed MB/s 1260.0558679162832

I understand std is using copy_file_range syscall but why is it such a big difference and can't it be improved?

[Darksonn]

I explain this on the URLO thread that you also posted.