Windows does not have yes command.

Yep, I don't have a yes command in cmd. However there is one in Git bash, (default location C:\Program Files\Git\usr\bin\yes.exe), which may be in your CMD path by default, causing one to think there's one built in. Obviously we can't depend on it being there though.

Note: while … echo itself pipes at 1 MiB/s for a 5-char msg and 70 MiB/s for a 4096-char msg, while yes pipes at 8 GiB/s for the same 5-char msg and 5 GiB/s for a 4096-char msg.

So this could reduce the slowdown (or the cpu usage) introduced by the test itself here. Not sure if that effect is measurable, though.

This significantly affects the benchmark (in a positive way).

Before:

$ node benchmark/child_process/child-process-exec-stdout.js
child_process/child-process-exec-stdout.js dur=5 len=64: 40872.31295343989
child_process/child-process-exec-stdout.js dur=5 len=256: 42284.49284876121
child_process/child-process-exec-stdout.js dur=5 len=1024: 42556.261440065464
child_process/child-process-exec-stdout.js dur=5 len=4096: 40866.002162569785
child_process/child-process-exec-stdout.js dur=5 len=32768: 45769.970852308645

After:

$ node benchmark/child_process/child-process-exec-stdout.js
child_process/child-process-exec-stdout.js dur=5 len=64: 52294.7307645832
child_process/child-process-exec-stdout.js dur=5 len=256: 51257.097720466736
child_process/child-process-exec-stdout.js dur=5 len=1024: 50287.9926165738
child_process/child-process-exec-stdout.js dur=5 len=4096: 52306.85402878927
child_process/child-process-exec-stdout.js dur=5 len=32768: 52307.0022664649

CI: https://ci.nodejs.org/job/node-test-pull-request/4227/

the CI not happy.

I've run the CI again: https://ci.nodejs.org/job/node-test-commit/5258/. It is still not happy. Anyhow, none of those failures are related.

Regarding yes - yes, it is not available by default under Windows, and needs to be installed by the user. I've experimented with shell and python scripts but they were much slower than yes.

@bzoz Is there any documentation for the requirements for running benchmarks on Windows? It would be helpful to document the need for a non-standard exe on the system (maybe in https://github.com/nodejs/node/tree/master/benchmark#prerequisites ?).

It would also make sense to have a comment above this line saying that this requires a yes.exe binary, e.g. the one in Git for Windows.

@gibfahn This is already mentioned in https://github.com/nodejs/node/blob/master/BUILDING.md#windows, but yes, we should also add this to https://github.com/nodejs/node/tree/master/benchmark#prerequisites.

Landed in d5bc52a