Bug 78611 - iwlwifi performance down to 40% with kernel 3.14 or kernel 3.15
Summary: iwlwifi performance down to 40% with kernel 3.14 or kernel 3.15
Status: CLOSED INVALID
Alias: None
Product: Drivers
Classification: Unclassified
Component: network-wireless (show other bugs)
Hardware: x86-64 Linux
: P1 normal
Assignee: drivers_network-wireless@kernel-bugs.osdl.org
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2014-06-21 22:17 UTC by M.Traxler
Modified: 2014-06-23 18:54 UTC (History)
2 users (show)

See Also:
Kernel Version: 3.15.1-34.2.gee8dd2b
Subsystem:
Regression: No
Bisected commit-id:


Attachments

Description M.Traxler 2014-06-21 22:17:14 UTC
When I upgrade OpenSuSE13.1 to the kernel 3.14 or 3.15 from factory or the
kernel-stable repository, the performance of my Intel Advanced-N 6205 using the /lib/firmware/iwlwifi-6000g2a-6.ucode firmware drops from
the normally reached
24MBytes/s down to 9MBytes/s.

No other change at all to the OpenSuSE13.1 installation, just exchanging the
kernel.

This has been reproduced on two different computers, both using iwlwifi.
computer a:
03:00.0 Network controller: Intel Corporation Centrino Advanced-N 6205 [Taylor Peak] (rev 34)
computer b:
0c:00.0 Network controller: Intel Corporation Centrino Advanced-N 6200 (rev 35)

The bitrate of ~300Mbits/s shown in wavemon is not affected by this problem.
Just the reached throughput is down to 40% of the old performance.

The throughput of the ethernet-network is not affected (at least not <50MBytes/s which I tested.)
I also checked various TCP-parameters, but no improvement was reached, even with the following parameters.

net.core.rmem_max = 67108864
net.ipv4.tcp_rmem = 4096 87380 67108864
net.core.netdev_max_backlog = 250000
net.ipv4.tcp_congestion_control=htcp

Both, OpenSuSE13.1 and OpenSuSE13.1 with tumbleweed show the problem.
With kernel-desktop-3.11.10-11.1 everything is fine.
With kernel-desktop-3.15.1-34.2.gee8dd2b is see the performance issues.
The same performance drop is seen with kernel-default-3.14 and kernel-default-3.15.
The wireless-accesspoint is a TP-Link TL-WDR3600.

Thanks a lot!
Comment 1 Emmanuel Grumbach 2014-06-23 16:18:48 UTC
Please try to add 11n_disable=8 to iwlwifi
Comment 2 M.Traxler 2014-06-23 18:05:30 UTC
Yes, this solves the problem!
Now I also have 24-26MBytes/s throughput with the kernel 3.15.

Thanks a lot for helping me out here!

Michael

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