Clock skew detected during build #8318
Description
Version
Microsoft Windows [Version 10.0.19042.1348]
WSL Version
- WSL 2
- WSL 1
Kernel Version
5.10.102.1
Distro Version
Ubuntu 20.04.4 LTS
Other Software
No response
Repro Steps
When building a kernel I would often get multiple clock skew errors as has been discussed in prior bugs such as #4975 when performing a:
sudo make -j 8
During compile my Vmmem and COM Surrogate processes are taking up close to 100% of my CPU cycles.
This is on a i7-3820QM:
bengalih@MOBILEONE:/mnt/c/Users/bengalih$ getconf _NPROCESSORS_ONLN
8
As my system date/time appears normal when starting the build process, I theorized that the heavy hit to the CPU may have been contributing to a small clock drift during compile time. I tested this theory by running with:
sudo make -j 6
I performed at least 3 builds each using 6 and 8 respectively and without fail the clock skew error appeared when using the full 8 core, but never when I ran with 6.
(EDIT: On last build with "6" I did get one skew error when I also opened a zoom meeting on my device during build. This was an anomaly as on all other 6 builds I did not get any skew and on the 8 runs I would get multiple per run).
While this is not a "bug" per-se, many people seeing this issue at build time may be in a similar situation where they are using slightly older processors. However, it may be considered a bug that the kernel scheduler is not reserving cycles for keeping time in sync (as there have been reported other clock skew issues outside of just build).
I wanted to give this as a PSA for others having the issue, and maybe a more official note can be made somewhere, perhaps in the build instructions:
Expected Behavior
clock can remain in sync even when running highly CPU intensive tasks.
Actual Behavior
clock appears to lose time when running highly CPU intensive tasks.
Diagnostic Logs
make[3]: warning: Clock skew detected. Your build may be incomplete.