I have similar problems with my Intel 7260 wifi and did some research on how to fix these issues.
It turns out that lots of people have problems with this wifi card and its related driver the iwlwifi. However, it seems there is no easy apply and forget fix as people are reporting different problems (also due to different APs being used of course). Hence, some testing is has to be done.
The following links should be helpful:
I found several related bug reports on launchpad, see here, here, here, and here.
Furthermore, on the Archwiki there is a useful troubleshooting section for the iwlwifi driver.
Last but not least here is also a brief summary on how to fix iwlwifi related problems.
Some suggested solutions are:
- Turn off bluetooth (use rfkill or turn off in Bios)
- Turn OFF 802.11n mode (in /etc/modprobe.d/iwlwifi.conf add options iwlwifi 11n_disable=1)
- Turn ON link aggregation (in /etc/modprobe.d/iwlwifi.conf add options iwlwifi 11n_disable=8)
- Turn OFF watchdog (in /etc/modprobe.d/iwlwifi.conf add options iwlwifi wd_disable=1)
- Turn off power saving features ($ sudo iw wlan0 set power_save off)
- Set regulatory domain ($ sudo iw reg set <country code>)
In my case the stability problems were coming from frequent disconnects showing up in the syslog (-> dmesg) as follows:
wlan0: deauthenticating from ....... by local choice (Reason: 3=DEAUTH_LEAVING)
I am running Ubuntu 15.04 (x64) with a 3.19 Linux kernel.
In my case it seems that the problems are fixed just by turning on link aggregation (11n_disable=8). Turning off power saving also seems to help. This holds for the 2.4GHz network.
For the 5GHz network I could not solve the problems and the link is highly unstable.
For how to turn off wifi power management permanently see here and here.
This ended up being what I believe to be a kernel bug. Upon updating to 4.0.0-040000-generic #201504121935 my CPU wait has been normal and system load under .10 in most cases unless something is happening on the hosted servers.
Anyway, I used the following link to help : http://ubuntuhandbook.org/index.php/2015/04/upgrade-to-linux-kernel-4-0-in-ubuntu/
and just to keep in compliance with the rules, I did the following as root and then rebooted the machine:
wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.0-vivid/linux-headers-4.0.0-040000_4.0.0-040000.201504121935_all.deb
wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.0-vivid/linux-image-4.0.0-040000-generic_4.0.0-040000.201504121935_amd64.deb
wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.0-vivid/linux-headers-4.0.0-040000-generic_4.0.0-040000.201504121935_amd64.deb
dpkg -i linux-headers-4.0.0*.deb linux-image-4.0.0*.deb
update-grub
As far as how I came to this - after reading through countless forums and newsgroups/mailing lists and getting nowhere (tried messing with BIOs, boot options, commit=60, disabling services, changing physical server location, etc.) I decided to either downgrade or update the kernel...being that 15.04 is new I updated. Still unsure the root cause as I haven't seen any other reports of this issue, my assumption is when I used rsync from my old 14.10 system a faulty driver was copied over or a faulty kernel file - why 4.0.0 fixes this is beyond me...but at least no more kworker writing every 5 seconds to kern.log and my harddrives.
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