GNOME Bugzilla – Bug 581412
Performance issue with AP scanning
Last modified: 2009-05-10 02:38:40 UTC
Please describe the problem: Hi guys, I want the ability to turn off AP scanning for NM. I have an rt2670 chipset wireless N card and I have good signal strength. When I ping flood my router, I get ~10 MByte/sec to and from it consistently until NM decides to scan for other APs. Then my throughput drops to zero for approximately 5 seconds (the incident occurs approx. ever 100 seconds.. magic number?). Given that many netbooks utilize this same chipset, it may be helpful to have this option. Since I couldn't find a way to disable scanning in a config file, I uninstalled it and installed wicd which works perfectly and I don't get the bad throughput drops. I realize this is mostly likely due to poor performance in the driver but it is still making NetworkManager unusable for me. Steps to reproduce: 1. ping router 2. watch throughput of wireless connection 3. watch syslog for "kernel: [ 1167.024540] ===>rt_ioctl_giwscan. 3(3) BSS returned, data->length = 560" messages every 100 seconds which immediately appear after a session of zero throughput for a duration of around 5 seconds Actual results: Every 100 seconds, I get zero throughput for a duration of 5 seconds, then it goes back to normal operation. Expected results: I would expect no AP scanning to occur when I am connected to a wireless network. (or at least a way to turn this off). Does this happen every time? Yes! Other information: Ubuntu 9.04 x86_64, rt2670 with driver v2.1.1 wireless BTW, in your FAQ for NM, you say that you do AP scanning in a way that impacts the card the most. I believe you. :)
AP scanning actually has little real effect, and does not use much power at all. What's the actual objection here, that your transfer rate drops momentarily every so often when NM scans?
Thanks for getting back with me. > What's the actual objection here, that your transfer rate drops > momentarily every so often when NM scans? Exactly, transfer rates dropping = bad. It is really frustrating when doing latency sensitive tasks like VoIP or online gaming. Think of a 5 second lull in your VoIP call every 100 seconds, or a 5 second pause in a first person shooter (certain death). I don't care about power really since this is in a desktop environment. I am not even 100% sure that the AP scanning is causing the issue I just noticed a correlation between the lull and the log message. I also noticed the symptom go away when I removed NetworkManager and installed wicd. If you have other things I can try, I would be glad to help. I like NetworkManager (and would like to go back) but its unusable for me in its current implementation.
*** This bug has been marked as a duplicate of 513820 ***