After the last stable update I got a serious performance problem with the USB WiFI dongle that I normally use with my notebook: a D-Link DWA 131 based on RTL8192EU chip.
IMO the problem is generated from the power management (powerdevil or something else, I didn’t investigte till now) and the final result is that the performance make the WiFI connection unusable.
The solution I found googling around is to generate the file
and to add this command line:
options 8192eu rtw_power_mgnt=0 rtw_enusbss=0
After the reboot all work correctly. I tested it also with the rtl8192cu and work.
rtwp_power_mgnt=0 disable the power management
rtw_enusbss=0 disables USB autosuspend
I found the solution here: https://github.com/xbianonpi/xbian/issues/217
EDIT 0: I continue to investigate cause I’m having an annoying message in dmesg, continuously replicated with the shortGIrate value jumping between 0 and 1. The message is:
RTL871X: rtl8192e_set_raid_cmd, bitmap=0xf8ff000, mac_id=0x0, raid=0x0, shortGIrate=1
Looking around I discover that:
- is possible to see the parameters implemented in the driver; the command is modinfo . For me:
But is also possible to see the VALUE of the parameters with the command systool -v -m . For me:
systool -v -m 8192eu
I wasn’t able, till now, to avoid the message (I think its trying to jump between different WiFI frequency, 2GHz/5GHz, or to jump between different WiFI Access Point; we have 2 in office), but the performance are definitely better. I added also another parameter to the /etc/modprobe.d/8192eu.conf to definitely disable the power management. Not the 8192eu.conf is:
# Disable power management options 8192eu rtw_power_mgnt=0 # Disable USB autosuspend options 8192eu rtw_enusbss=0 # Disable power management (Gentoo forum for 8192ce) options 8192eu rtw_ips_mode=0
I’ll continue to investigate the parameters cause I’ve the “sensation” that setting correctly some parameters I can solve the problem definitely and to have better performance. If somebody know where to find a place explaining what do these parameters, should be a great help.
EDIT 1: in the meantime I discovered the C function that define and manage the shortGIrate variable and yes, I’m almost sure that its part of the code that control the connection rate (2GHz or 5GHz). Now, after the configuration file, I’ve less messages in the log and (almost) all always with the “1” value, while before the value jumped between “1” and “0”. Now I must discover HOW to avoid that the driver, after some minutes, try to modify the connection frequency when its connected to the same AP/Router.
EDIT 2: now the performance are like before the upgrade and better. I modified the configuration file using ONLY the first 2 parameters. Now the 8192eu.conf file is:
# Disable power management options 8192eu rtw_power_mgnt=0 # Disable USB autosuspend options 8192eu rtw_enusbss=0 # Disable power management (Gentoo forum for 8192ce) # options 8192eu rtw_ips_mode=0
In the meantime I upgraded also the router firmware and modify also the DHCP lease time of the router; just to avoid unusable negotiation to confirm an internal IP address.