On Fri, Apr 7, 2017 at 5:37 PM, Thomas Daede bztdlinux@gmail.com wrote:
There's also tuned, another way to set lots of kernel bits. I think it was an accepted feature for a previous Fedora release, but it's off by default, and it is only mentioned in the Fedora 20 power saving guide, which seems to have disappeared entirely for Fedora 21+:
https://docs.fedoraproject.org/en-US/Fedora/20/html/Power_Management_Guide/t...
It would be really nice to have something on by default. I certainly don't want to go through the laundry list of tunables and profiles every time I install a Fedora system. The big thing that has prevented this previously, as I understand, is the possibility to expose power management bugs, breaking things for some users.
In my experience some of the powertop settings make quite a big difference. Out of the box on my haswell laptop, Fedora never enters any package state lower than C2. Just turning on SATA link power management, for example, allows it to enter C3 and saves a few watts.
Thermald is claimed by Intel to be mature, so that seems pretty straight forward. I wonder if that'll put it in C3, or if that just tames things down when the CPU starts to get warm (why the kernel doesn't do this or the CPU itself I do not understand but beside the point).
Powertop, maybe it ought to be a feature request for F27, and see if a bunch of bug reports happen during the beta *shrug*. I've used it on an ancient and new laptop, of different manufacture, and haven't had a problem. But of course if it puts e.g. USB bus to sleep and there's a bug preventing it from waking up when someone plugs a flash drive in, that'd be pretty annoying as default behavior if this is a possibility.