100% CPU usage for a long time after execution of the last statement
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- JavaScript
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Description
Version
v12.x-v20.x - severe, v8.x - v10.x - less severe but still visible
Platform
Darwin Andreys-MacBook-Pro.local 22.2.0 Darwin Kernel Version 22.2.0: Fri Nov 11 02:03:51 PST 2022; root:xnu-8792.61.2~4/RELEASE_ARM64_T6000 arm64
Subsystem
suspect GC
What steps will reproduce the bug?
run first script in the gist: https://gist.github.com/sidorares/128160e6b3dea1da3ad45cd672651d2d#file-repro1-js
After last line console.log("done"); is executed CPU spikes to 100% and stays like that for about 5 minutes.
In case of node v8 and v10 cpu spike is much shorter, 5-7 seconds.
Bun.js executes the script almost instantly
How often does it reproduce? Is there a required condition?
Consistently reproduceable
What is the expected behavior? Why is that the expected behavior?
the script is expected to finish in sub second time
What do you see instead?
CPU spikes for 300-400 seconds which is unexpected for the workload
Additional information
The profiler only reports the code before the CPU spike, no high GC usage, the time after cpu spike is "unaccounted".
[Shared libraries]:
ticks total nonlib name
98 0.0% /Users/laplace/.nvm/versions/node/v20.3.0/bin/node
[JavaScript]:
ticks total nonlib name
2 0.0% 0.0% JS: *parseLengthCodedInt /Users/laplace/tmp/2090/repro3.js:2014:24
[C++]:
ticks total nonlib name
[Summary]:
ticks total nonlib name
2 0.0% 0.0% JavaScript
0 0.0% 0.0% C++
66 0.0% 0.0% GC
98 0.0% Shared libraries
291682 100.0% Unaccounted
[C++ entry points]:
ticks cpp total name
[Bottom up (heavy) profile]:
Note: percentage shows a share of a particular caller in the total
amount of its parent calls.
Callers occupying less than 1.0% are not shown.
ticks parent name
291682 100.0% UNKNOWN
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 by running the first script in the linked gist on the affected Node.js versions and compare its behavior with Node.js v8-v10 and Bun.js. Use the reported profiler output and reproduction timing to investigate the post-console.log CPU spike; done means the script exits in under a second without the sustained CPU usage.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- node.js
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100