This bug has a concrete real-world consequence documented in LP: #2156368.
On Ubuntu 24.04.4 (thermald 2.5.6-2ubuntu0.24.04.3) with an Intel Core Ultra 7
265KF (Arrow Lake, family 6:198:2), thermald invokes intel_powerclamp on all 20
CPU cores at approximately 50% duty cycle immediately at boot, despite CPU
temperatures of 28–32°C against a high threshold of 85°C. No thermal-conf.xml
is present; thermald logs its absence and proceeds to throttle anyway in
adaptive mode.
The measured impact is an 85% reduction in memory bandwidth: STREAM Triad drops
from 76,805 MB/s (correct) to 6,500 MB/s (throttled). Real-world compute
workloads are degraded proportionally.
Note that LP: #2087816 was marked Fix Released and addressed Arrow Lake CPU ID
recognition (making thermald active on Arrow Lake). That is a separate issue
from the behavior described here, where thermald correctly recognizes Arrow
Lake but then aggressively throttles it with no platform configuration present.
The upstream README suggests two potentially relevant fixes not yet present in
Noble: Release 2.5.7 ("Seg fault when no config file for the first time") and
Release 2.5.12-rc1 ("adaptive-mode behavior was tightened: fail/exit paths,
ignore-default-control handling"). The latter in particular appears directly
relevant to this failure mode.
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https://bugs.launchpad.net/bugs/2085600
Title:
Support Intel Lunarlake and Arrowlake platform
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