Node: CPU time passes 10x faster than real time on a single core

[tniessen]

• Version: v13.11.0
• Platform: Linux 4.15.0-91-generic #92-Ubuntu SMP x86_64 x86_64 x86_64 GNU/Linux
• Subsystem: os

What steps will reproduce the bug?

const { cpus } = require('os');
const measure = () => cpus().map(c => c.times.idle);
const diff = (first, second) => second.map((v, i) => v - first[i]);
setTimeout(((first) => () => console.log(diff(first, measure())))(measure()), 1000);

How often does it reproduce? Is there a required condition?

Always.

What is the expected behavior?

Within 1000ms, each core cannot spend more than (approximately) 1000ms idle.

What do you see instead?

[
  10200, 10200,
  10100, 10200,
  10000, 10000,
   9900, 10000
]

Additional information

I cannot reproduce the problem on Windows, so I assumed it's a problem in libuv, but the code in libuv seems correct to me.

[bnoordhuis]

That was actually fixed just three days ago, see libuv/libuv@37a8aff. :-)

[tniessen]

@bnoordhuis Oh, nice! That explains it :D Any idea when that patch might make it into a Node.js release?

[bnoordhuis]

Probably sometime in May. The last libuv release was just last week.

[jasnell]

I believe this has been resolved in master