Bug 44627

Summary: readahead and journal-commit waste power
Product: pm-utils Reporter: Martin Pitt <martin.pitt>
Component: GeneralAssignee: Richard Hughes <richard>
Status: RESOLVED WONTFIX QA Contact:
Severity: normal    
Priority: medium CC: colin.king
Version: unspecified   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:

Description Martin Pitt 2012-01-10 03:42:20 UTC 
From https://launchpad.net/bugs/900923:

Colin King spent some days doing extensive and accurate power benchmarking [1], amongst others the effect of the pm-utils power.d scripts on various machines [2].

It turns out that the readahead and the journal-commit scripts do not actually save power these days (maybe they did at the time when they got introduced, but changes in the kernel nullified them?). No measurable difference on HDD, and on SSD power usage increases by 1.5%. This was confirmed on an idle system, on a system doing compiling/package build, and a workload with music playback and browsing, each 5 times over 60 minutes.

Based on this it seems that these scripts should be disabled by default or removed.

[1] http://zinc.canonical.com/~cking/power-benchmarking/
[2] http://zinc.canonical.com/~cking/power-benchmarking/pm-utils-results/
Comment 1 Adam Jackson 2018-06-29 19:57:10 UTC 
pm-utils hasn't been touched in eight years, none of this is likely to get addressed. Closing bugs and disabling the bz product.

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