Software - iwlwifi slow with kernel 3.4!?

l1n00x - 14.06.2012, 15:27
Post subject: iwlwifi slow with kernel 3.4!?

I just noticed that the transfer speed on my Intel Corporation Centrino Advanced-N 6205 (rev 34) is quite slow with the two recent 3.4 kernels. I do not know about earlier 3.4 kernels, though. The speed is around [2.0, 4.0] MiB/s. I've switched to kernel 3.3-6.slh.1-aptosid-amd64 which gives me around [4.0, 5.0] MiB/s. With the 3.3 Kernel the bitrate goes up to 300Mbit/s and stays at 270Mbit/s most of the time (5 MiB/s is also way too slow for 802.11n). On 3.4 the bitrate goes up and down between 150Mbit/s and lover values and even drops down to 1Mbit/s.


Host/Kernel/OS  "aptosid-x220" running Linux 3.4-2.slh.2-aptosid-amd64 x86_64 [ aptosid 2011-03 Πόνος - kde-lite - (201112312100) ]
CPU Info        4x Intel Core i5-2520M @ 3072 KB cache flags( sse3 ht nx lm vmx ) clocked at [ 800.000 MHz ]
Videocard       Intel 2nd Generation Core Processor Family Integrated Graphics Controller     [  ]
Network cards   Intel 82579LM Gigabit
                Intel Centrino Advanced-N 6205
Processes 162 | Uptime 14min | Memory 725.4/7767.4MB | HDD M4-CT128M4SSD2,External Size 448GB (40%used) | Client Shell | Infobash v3.45

I'm not sure if this is an upstream issue or caused by slh's kernel modifications as I do not have a 3.4 vanilla kernel compiled. Did anyone also notice this problem?

EDIT: BTW, I'm using 11n on auto channel on my OpenWRT 10.03.1 router!

EDIT 2: rmmod iwlwifi ; modprobe iwlwifi 11n_disable=1 give me a stable data rate of 54Mbit/s on the 3.3 kernel and 24mbit/s with the 3.4 kernel. According to this, it's not a problem with the 11n mode.
With the 3.4 kernel (no 11n_disabled=1), the bitrate jumps from 150mbit/s to 1mbit/s and everything in between.
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