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SubjectRe: 2.6.38: rt2800usb: high latency (1000ms)?


On Wed, 13 Apr 2011, Daniel Halperin wrote:

> On Wed, Apr 13, 2011 at 1:13 PM, Justin Piszcz <jpiszcz@lucidpixels.com> wrote:
>>> (1) What is the AP's beacon period and DTIM? Typical values are 100
>>> TUs for beacons (102.4 ms) and 2 for DTIM (2 beacons per power-save
>>> wakeup) which should imply a mean of 100 and max of 200 ms delay even
>>> on pings.
>>
>> I am using a WNDR3700 with default settings in terms of beacons/etc.  No
>> issues with any device (laptop, computer, etc (in windows)), I have two
>> wireless USB adapters (bought two) and in Windows, no problems, I don't
>> think
>> it is the WNDR3700.  As far as linux/wpa-supplicant, using default settings.
>
> Not enough info. What does "iw dev wlan1 scan dump" (it might not be
> wlan1 for you) say for "beacon interval"?

# iw dev wlan0 scan dump

BSS (hidden) (on wlan0) -- associated
TSF: 103430650682 usec (1d, 04:43:50)
freq: 2417
beacon interval: 100
capability: ESS Privacy ShortPreamble ShortSlotTime (0x0431)
signal: -59.00 dBm
last seen: 1345742 ms ago
SSID: (hidden)
Supported rates: 1.0* 2.0* 5.5* 11.0* 6.0 9.0 12.0 18.0
DS Parameter set: channel 2
RSN: * Version: 1
* Group cipher: TKIP
* Pairwise ciphers: CCMP TKIP
* Authentication suites: PSK
* Capabilities: (0x0000)
WPA: * Version: 1
* Group cipher: TKIP
* Pairwise ciphers: CCMP TKIP
* Authentication suites: PSK
ERP: <no flags>
Extended supported rates: 24.0 36.0 48.0 54.0
WMM: * Parameter version 1
* u-APSD
* BE: CW 15-1023, AIFSN 3
* BK: CW 15-1023, AIFSN 7
* VI: CW 7-15, AIFSN 2, TXOP 3008 usec
* VO: acm CW 3-7, AIFSN 2, TXOP 1504 usec
HT capabilities:
Capabilities: 0x11ce
HT20/HT40
SM Power Save disabled
RX HT40 SGI
TX STBC
RX STBC 1-stream
Max AMSDU length: 7935 bytes
DSSS/CCK HT40
Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
Minimum RX AMPDU time spacing: 1/2 usec (0x02)
HT RX MCS rate indexes supported: 0-15
HT TX MCS rate indexes are undefined
WPS: * Version: 1.0
* Manufacturer: Netgear, Inc.
* Model: WNDR3700
* Device name: (hidden)
* Config methods: Ethernet, Label, PBC
> Does anyone know how to get the DTIM period out of iw?
>
>>> (2) How long does the client wait after waking up to go back to sleep?
>>> It should be at least a few seconds. For ssh, then, you should see
>>> something like a 100-200 ms delay for the first key and then nothing
>>> at all unless you stop typing for a bit.
>>
>> It lags with each word I type, it is terrible.  If I run something like
>> dmesg or ps auxww, the entire session freezes for 5-10 seconds before it
>> comes back.
>
> Sorry; I meant what is the software stack configured to do? Do some
> looking around.
>
>>> I'm SSHing over a Wi-Fi link that uses power save right this second,
>>> and have for years. It's not generally an issue, I suspect something
>>> worse is going on.
>>
>> Maybe the wireless usb adapters do not function well in Linux with power
>> save
>> on.
>>
>> I bought them awhile ago, they had the highest reviews, and in Windows,
>> they did do 10-15MiB/s, in Linux, I see ~4.6MiB/s (but that was with power
>> save on) about the same, 4.5MiB/s.
>> http://www.amazon.com/Medialink-Wireless-Adapter-802-11n-Compatible/dp/B002RM08RE
>
> Yeah, these might indicate a fairly sizable problem in the Linux drivers IMO.
>
> Dan
>
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