swc-project
High Idle CPU Usage
Describe the bug
The issue https://github.com/swc-project/swc/issues/10243 still persists even in the latest version:
cat go.js
require("@swc-node/register");
require("./test");
cat test.ts
class Test {
a;
b;
c;
d;
e;
f;
g;
h;
i;
j;
k;
l;
m;
n;
o;
p;
q;
r;
s;
t;
u;
v;
w;
x;
y;
z;
constructor() {}
hello() {
return 'HELLO';
}
}
setTimeout(() => {}, 20 * 1000); // to make the process run for 20 seconds
cat package.json
{
"dependencies": {
"@swc-node/register": "^1.10.10",
"@swc/core": "^1.11.24"
}
}
With 1.11.24:
/usr/bin/time -v node go.js
Command being timed: "node go.js"
User time (seconds): 2.73
System time (seconds): 0.81
Percent of CPU this job got: 17%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:20.32
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 156620
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 15834
Voluntary context switches: 1125721
Involuntary context switches: 133
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
With 1.10.8:
/usr/bin/time -v node go.js
Command being timed: "node go.js"
User time (seconds): 0.33
System time (seconds): 0.07
Percent of CPU this job got: 2%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:20.32
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 131564
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 14030
Voluntary context switches: 175
Involuntary context switches: 17
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
As you can see, the process constantly uses 15% CPU (2.7s of CPU time in 20s) while in 1.10.8 it only uses 2% cpu (0.33s in 20s), all of which is during transpilation (0% during idle).
No swcrc file is present.
CPU usage seems to proportionally rise the more properties the class has.
Link to the code that reproduces this issue
https://play.swc.rs/?version=1.11.24&code=H4sIAAAAAAAAAx3Pyw6CQAwF0P18RXeAMWF0S3Rn4oLEDT%2BAUAR5DM50fBH%2B3bluTtqk7U1VNZTOUcFOaFFEZRa4ggrUgEEDbqAFHbiDHgxgBBMwYAYPYIEDAjx4ghd4gw%2F4%2FnPN5MT6SoyNE1pWJPIwGDShDtdYvJ0oOp%2Fy%2FBJhZVWrUsqxFN3IxkscZg%2FHsLulvaYN7bTWSUZpSmJoLHsmaZlmayoOv1s%2FUWMsRh2H9Nr9AO8kjXIVAQAA&config=H4sIAAAAAAAAA1VQOw6DMAzdOQXy3LUdeocewkoNCiIf2Y5UhLh7E0Io3ez38bO9dn0Pkxh49msucxORhfjsMyKLV%2FxkBHSJJIZtVLg1VqVQyol2ZKsEKPJIWkwk90MNcwhCGRtwFmpCRi9DYFcigQmNXsM5ebWumACTBodqDdSkFuWst8NyNZngIpPIf1SRoh%2Fnc4M6pjuWBhfeaSePT5Rr6wEP%2BIla2DkYrLyac3%2FD9gW9JRc9VQEAAA%3D%3D
SWC Info output
Operating System:
Platform: linux
Arch: x64
Machine Type: x86_64
Version: #1 SMP PREEMPT_DYNAMIC Thu, 13 Mar 2025 18:12:00 +0000
CPU: (16 cores)
Models: AMD Ryzen 7 7840U w/ Radeon 780M Graphics
Binaries:
Node: 23.9.0
npm: 11.3.0
Yarn: 4.7.0
pnpm: N/A
Relevant Packages:
@swc/core: 1.11.24
@swc/helpers: N/A
@swc/types: 0.1.21
typescript: 5.8.3
SWC Config:
output: N/A
.swcrc path: N/A
Next.js info:
output: N/A
Expected behavior
No CPU usage
Actual behavior
High CPU usage on idle (even after transpilation done)
Version
1.11.24
Additional context
No response
Also note the Voluntary context switches: 1125721 and the higher memory usage.
Sure, here you go: https://gist.github.com/phiresky/e3d3dff24ff495552971dda945521b84
git clone https://gist.github.com/phiresky/e3d3dff24ff495552971dda945521b84
cd e3d3dff24ff495552971dda945521b84
npm install
node go.js
I find that the heartbeats in chili scopes are not dropped so https://github.com/dragostis/chili/blob/6c49338d25f1656ba1cdd0b9b21479cd4207652f/src/lib.rs#L152 is always running and calling HashMap::retain (l.heartbeats.len() == num_workers is always false because there are extra scoped heartbeats).
I believe something wrong with https://github.com/dudykr/ddbase/blob/b092d7ca474c3cc30816bd2a416bfe1689b85883/crates/par-core/src/lib.rs#L182, which prevents scopes being dropped. The problem is solved when I remove SCOPE.set(Some(scope));, but I'm not sure whether this is correct. cc @kdy1
This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.
