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I'm connecting to computer Y on my wireless LAN at home. Y is a newly-assembled machine running Kubuntu 14.04; it's wireless adapter is "Realtek RTL8192CE PCIe (rev 01)". Between other machines on the WLAN I get reasonable behavior, no strange delays etc (specifically, typing in a terminal over an SSH connection is responsive). However, when SSHing to Y, the establishing the connection takes longer than expected, and later on there are occasional delays between the time a key was pressed and the time it shows up on screen. 'lag', if you will. Except that it is inconsistent, and sometimes the lag goes away for a few seconds and resumes again.
I'm not seeing something particularly interesting in the logs, but I may well be overlooking a hint somewhere.
My suspicion is that this has something to do with the network stack, maybe the wireless driver. What can I do to pinpoint the problem?
Notes:
- Seeing timeouts also when using CIFS/SMB.
- Another machine that is very close-by doesn't exhibit the same behavior when I connect to it.
- Load average is very low, the machine is mostly idle.
- Just tried connecting machine Y with Ethernet to one of my other machines - and that makes the problem go away (!). I still want to connect via WLAN though.
Contents of /proc/lan/wireless:
Inter-| sta-| Quality | Discarded packets | Missed | WE
face | tus | link level noise | nwid crypt frag retry misc | beacon | 22
wlan0: 0000 46. -64. -256 0 0 0 0 4313 0
link ranges from 34 to 58, level from -246 to -50, noise is -256 all the time. Discarded packets figure is for 7.5 hours of uptime.
top 4 powertop entries:
Usage Events/s Category Description
1.4 ms/s 101.2 Process kwin -session 10146e4d
3.7 ms/s 33.6 Process /usr/lib/firefox/firef
640.7 µs/s 32.4 Process /usr/bin/java -Dosgi.r
48.8 µs/s 21.7 kWork ieee80211_iface_work
einpoklum
Posted 2015-04-25T16:30:54.060
Reputation: 5 032
1There are some other machines that use the same wireless channel, example Microwaves, TV signal repeaters, etc. You can start by checking the wireless signal with:
watch -n 1 cat /proc/net/wireless< – cfreire – 2015-04-25T18:15:36.817
@cfreire: Added results of that to the question. – einpoklum – 2015-04-25T18:35:20.907
Apparently you have a poor WI-fi connection (link 34 / level -256) good values (link 70 / level -30). Noise -256 indicates no outside interference. Try, if possible move equipment to increase these values – cfreire – 2015-04-25T19:00:12.457
@cfreire: Playing with the antennae and moving the box around improves the values - but behavior remains the same. – einpoklum – 2015-04-25T19:09:49.770
OK. In another direction. Is your loadvg (first value) above the number of cores?
watch -n -1 cat /proc/loadavg< – cfreire – 2015-04-25T19:19:21.723
1Can you try the conection with another link, ex. ethernet? – cfreire – 2015-04-25T19:25:03.013
@cfreire: Ethernet make the problem go away. Load average is very small (0.02), I don't do much with the box right now - just hooked it up... – einpoklum – 2015-04-25T19:39:31.333
If possible verify the power saving for the wireless link
powertop
and
iwlist wlan0 power< – cfreire – 2015-04-25T19:53:23.130
On #powertop (3TAB - STATS) see if wifi card is using all the power at 100% try disabe with #sudo iw wlan0 set power_save off – cfreire – 2015-04-25T20:16:36.853