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Slow WiFi on Fedora 26

asked 2017-09-23 15:01:28 -0500

r0dc gravatar image

updated 2017-09-23 16:37:59 -0500

Things had been working fine until the last week of two. Now my Fedora 26 Wifi runs at about 1/2 speed. My machine is dual boot and when running Windows 10 network speeds are at (or above) my ISPs stated speeds 5up/50down. But when running Fedora26 speeds are about 1/2 that, sometimes worse. I'm using OOKLA's and/or google's page that offers testing via mlabs, results are similar.

basic machine info:

lspci | grep -i net: 01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 0c) 02:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8821AE 802.11ac PCIe Wireless Network Adapter

lo no wireless extensions.

virbr0-nic no wireless extensions.

virbr0 no wireless extensions.

enp1s0 no wireless extensions.

wlp2s0 IEEE 802.11 ESSID:"moose&squirrel-5g"
Mode:Managed Frequency:5.805 GHz Access Point: A0:04:60:8A:B1:1A
Bit Rate=200 Mb/s Tx-Power=30 dBm
Retry short limit:7 RTS thr=2347 B Fragment thr:off Power Management:off Link Quality=61/70 Signal level=-49 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:1693 Missed beacon:0

uname -a:
Linux tower 4.12.13-300.fc26.x8664 #1 SMP Thu Sep 14 16:00:38 UTC 2017 x8664 x8664 x8664 GNU/Linux

Now I read a bunch about slow wifi in this Q&A support forum & searching the net. Nothing I've read about has helped, and much of it is 2-3 years old, or more.

I prepared a USB thumb drive with live Ubuntu and, surprise, wifi performed as expected! But I just can't nail down what is different between my Fedora system and Ubuntu....


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answered 2017-09-24 07:09:10 -0500

ozeszty gravatar image

Your WiFi driver is built into kernel, so it's where you should look first. What's the kernel version in tested Ubuntu?

Use dnf history list and dnf history info xxx (where xxx is an ID of update you want to check in detail) to determine after which installation WiFi slowed down. Boot kernel from before this installation, and if WiFi is back to normal, you know there's been a regression.

Test latest version, maybe it's been already fixed. If not, look through first regressed kernel changelog (sometimes it's easy to find culprit when you find a commit related to your problem) and report a bug.

If it wasn't kernel issue, use dnf history rollback xxx to remove all package changes (updates, installs and deletions) since before problematic update (with xxx ID), reboot and start installing network related packages one by one. When your issue reappears, you'll know against which component to report a bug.

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"What's the kernel version in tested Ubuntu?" Latest 16.04.3 LTS

"Your WiFi driver is built into kernel, so it's where you should look first.", Maybe, maybe not, could have been hardware, hence the window-10/Ubuntu tests I mentioned. (FWIW I tried a live environment of th latest Mint, it to performed slowly). So, with Windows & Ubuntu seemingly confirming that the HW is OK it was time for research to determine if the problem was known & possibly fixed. No joy. --MORE-

r0dc gravatar imager0dc ( 2017-09-24 10:50:31 -0500 )edit

Researching the net & this support forum I came to realize there are a fair number of config files that affect operation & performance of these modern Linux environments. But that soon led to the conclusion that it must be a kernel driver issue. And that brought me back here & the question I posted. Thanks for the tips on how to use DNF, it's just what I needed to dig deeper into this issue. The whole sysadmin environment is somewhat overwhealming to me after being away from Linux/Unix environments for 10+ years. Things have gotten a lot more sophisticated.

r0dc gravatar imager0dc ( 2017-09-24 11:05:49 -0500 )edit

Ubuntu definitely uses older kernel, maybe differences in iwconfig output between Ubuntu (or older Fedora kernel) and current Fedora will point you in some direction.

Welcome back on Linux, have fun hunting this regression!

ozeszty gravatar imageozeszty ( 2017-09-25 15:51:23 -0500 )edit

Think I got it. I went back to my initial install USB live environment. The kernel was 4.11.8-300.fc26.x8664, and networking worked perfectly. Using your earlier tips I saw a kernel change to 4.12.8-300.fc26.x86 64 about the time I started seeing problems. Looking at kernel change logs I saw some code changes involving RealTek (my WiFi NIC) devices. So I filed a bug report , already got a response, and things are looking good so far. Thanks for the help/tips on this one .

r0dc gravatar imager0dc ( 2017-09-25 17:27:46 -0500 )edit

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Asked: 2017-09-23 15:01:28 -0500

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Last updated: Sep 24 '17