Reported by Google Chrome/Chromium OS engineers a few weeks ago wereperformance regressions affecting CPU usage, power consumption, dropped frames in video playback tests, and other related performance issues. They tracked it down to a CPU idle change that was back-ported to the Linux 6.1 and 6.6 LTS kernels and other stable kernel branches.
It was tracked down to this commit for cpuidle aiming to avoid discarding useful information.The commit was merged to the Linux kernel earlier this year but where it became a problem was being back-ported to the stable Linux LTS kernels and then noticed by Google for regressing the performance on Intel Chromebooks. The regression appears to be primarily for Intel Jasper Lake based Chromebooks.
The fix is largely reverting that earlier code.
That fix was merged as part of this week's power management updates for Linux 6.18-rc3. In turn the Linux stable kernel branches in the coming days will hopefully be picking up this performance fix too.