I have a laptop with dual boot elementaryOS Loki and Windows 10. Until recently everything was fine, but now suddenly the wifi in elementaryOS is extremely slow (~0.5Mbit download, most speed tests don't even start the upload test). With Ethernet, I get the normal 80 MBit download. I also tried it with Windows where it's still 25 MBit via Wifi.
lspci -knn | grep Net -A2 01:00.0 Network controller : Intel Corporation Centrino Advanced-N 6235 [8086:088e] (rev 24) Subsystem: Intel Corporation Centrino Advanced-N 6235 AGN [8086:4060] Kernel driver in use: iwlwifi uname -a Linux tobias-530U3BI-530U4BI-530U4BH 4.10.0-38-generic #42~16.04.1-Ubuntu SMP Tue Oct 10 16:32:20 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux