Performance concern regarding print function

[UE2020]

The print function does not seem to implement block buffering. So if you print a lot of lines, you end up calling the write syscall for every line, which is quite costly.

[Alonely0]

false, print function collects all args and then prints them in a single syscall

Voila/src/interpreter/functions.rs

Line 61 in d259f22

// mitigate printing bottleneck by using only 1 print

[UE2020]

false, print function collects all args and then prints them in a single syscall

Voila/src/interpreter/functions.rs

Line 61 in d259f22

// mitigate printing bottleneck by using only 1 print

Line buffering and block buffering are not the same thing. Rust's io::stdout does not do block buffering by default.

rust-lang/rust#60673

[BlueCannonBall]

In C, setvbuf(stdout, NULL, _IOFBF, 0); can be used to make stdout block buffered. By default, it is line buffered.

[Alonely0]

ah lol, didn't know that. Tomorrow I'll patch it

[Alonely0]

These are the measures I made:

• stdout lock + write buffer
  ./target/debug/voila /home/guillem/ "1 == 1 {print(@name: @size=mb)}" -r 62.38s user 15.62s system 91% cpu 1:24.95 total

• stdout + write buffer
  ./target/debug/voila /home/guillem/ "1 == 1 {print(@name: @size=mb)}" -r 56.35s user 7.84s system 99% cpu 1:04.33 total

• stdout lock
  ./target/debug/voila /home/guillem/ "1 == 1 {print(@name: @size=mb)}" -r 54.93s user 8.20s system 99% cpu 1:03.28 total

• just print args joined
  ./target/debug/voila /home/guillem/ "1 == 1 {print(@name: @size=mb)}" -r 55.33s user 8.62s system 99% cpu 1:04.14 total

Stdout lock wins

[Alonely0]

98454e7