pm-utils reset the vm.dirty_ratio and vm.dirty_background_ratio variables

[Jean-Philippe Guérard]

On a desktop system, on AC power, pm-utils reset the vm.dirty_ratio and vm.dirty_background_ratio at boot time (which also reset the vm.dirty_bytes and vm.dirty_background_bytes variables).

When setting these variables using sysctl.conf, they are silently reset by the /usr/lib/pm-utils/power.d/laptop-mode script shipped with pm-utils.

The only way to give specific values to these variables using sysctl is to remove this script.

The default values applied by pm-utils are vm.dirty_background_ratio=5 and vm.dirty_ratio=10. On my 64-bits system with 16 GB RAM, this amounts to 1.6 GB for vm.dirty_bytes and 800 MB for vm.dirty_background_bytes (see http://lwn.net/Articles/572911/). These values are not reasonable for my system and pm-utils prevents me to change them.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: pm-utils 1.4.1-13ubuntu0.1 [modified: usr/lib/pm-utils/power.d/laptop-mode]
ProcVersionSignature: Ubuntu 3.13.0-44.73-generic 3.13.11-ckt12
Uname: Linux 3.13.0-44-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.14.1-0ubuntu3.6
Architecture: amd64
CurrentDesktop: XFCE
Date: Mon Jan 5 23:00:09 2015
PackageArchitecture: all
SourcePackage: pm-utils
UpgradeStatus: Upgraded to trusty on 2014-04-21 (259 days ago)