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[Bug 1039768] New: Failure to reduce frequency at low workload
  • From: bugzilla_noreply@xxxxxxxxxx
  • Date: Thu, 18 May 2017 15:31:33 +0000
  • Message-id: <bug-1039768-21960@http.bugzilla.opensuse.org/>
http://bugzilla.opensuse.org/show_bug.cgi?id=1039768


Bug ID: 1039768
Summary: Failure to reduce frequency at low workload
Classification: openSUSE
Product: openSUSE Tumbleweed
Version: Current
Hardware: x86-64
OS: Other
Status: NEW
Severity: Normal
Priority: P5 - None
Component: Basesystem
Assignee: bnc-team-screening@xxxxxxxxxxxxxxxxxxxxxx
Reporter: mpaton2000@xxxxxxxxx
QA Contact: qa-bugs@xxxxxxx
Found By: ---
Blocker: ---

Hardware is ASUS Laptop with Intel Core M3-6Y30 CPU, 8GB, passive cooling. Base
frequency=900MHz, Max Turbo=2.2GHz. Minimum frequency 400MHz.

Installed Tumbleweed x86_64 in December 2016, KDE desktop, btrfs root fs, no
extra repositories.

Problem is that after boot to KDE desktop, after initial set of root owned
housekeeping tasks finishes, and system workload goes down to less than 3% on
each core (from top and ksysguard), (2 physical cores, hyperthreaded),
frequency remains at around Max turbo, typically 2.2HGz on one core and 2.0GHz
on the other. Core temps stay high, and battery life halves.

I selected Tumbleweed in the hope of using the advanced power saving features
that this processor offers.

By chance, I discovered that when I boot from hibernation, a similar set of
root owned housekeeping runs, and then frequencies reduce to typically around
500MHz, with occasional brief spikes to 100MHz on a single core. This told me
that the kernel and the processor could indeed cooperate on selecting a low
frequency, as intended. However,something was being done on return from
hibernation that wasn't being done on initial boot, in order to enable this
behaviour.

This behaviour remained constant all the way through the 4.10.13 kernel.

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