performance.now() should jump after sleep/suspend/hibernation
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Description
Version
v18.14.2
Platform
Linux qubit 5.15.108-0-lts #1-Alpine SMP Fri, 21 Apr 2023 05:55:14 +0000 x86_64 GNU/Linux
Subsystem
perf_hooks
What steps will reproduce the bug?
In an interactive node session run:
function timeDelta() {
// The delta should be approximately the same on each invocation (assuming the system time is unchanged).
return Date.now() - performance.now();
};
const ref = timeDelta();
const before = timeDelta();
Now suspend and resume the machine / VM through whatever means. Then continue in the same node session:
const after = timeDelta();
console.log('BEFORE:', ref - before, 'AFTER:', ref - after);
Observe that the after value is incorrectly missing a number of seconds that matches the time the system was suspended. Eg. from my run:
BEFORE: -0.410888671875
AFTER: -7346.271728515625
How often does it reproduce? Is there a required condition?
100% (on Linux)
What is the expected behavior? Why is that the expected behavior?
performance.now() is expected to jump with the realtime passed time while suspended according to the spec and https://github.com/w3c/hr-time/issues/115.
The https://github.com/mdn/content/issues/4713 issue also goes into detail on how the "Ticking During Sleep" applies to various platforms.
What do you see instead?
No jump during sleep. Eg. by using more suitable clock reference, as proposed implemented in https://github.com/libuv/libuv/issues/1674.
Additional information
The current performance.now() implementation is based on process.hrtime():
This issue also seems to contain a lot of relevant context around a concrete problem: https://github.com/open-telemetry/opentelemetry-js/issues/852.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with lib/internal/perf/utils.js and the perf_hooks implementation, which currently bases performance.now() on process.hrtime(). Run the interactive Node session from the report around a system suspend or resume. Done means performance.now() advances by the elapsed suspended time on Linux while preserving the expected timeDelta behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, linux, node.js
- Domain
- performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Active
- Clarity
- Mostly clear
- Newbie friendliness
- 52/100