Bug 81571 - iwlwifi: Lack of TX AMPDU severely impacts performance
Summary: iwlwifi: Lack of TX AMPDU severely impacts performance
Status: CLOSED WILL_NOT_FIX
Alias: None
Product: Drivers
Classification: Unclassified
Component: network-wireless (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: drivers_network-wireless@kernel-bugs.osdl.org
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2014-08-02 17:37 UTC by haarp
Modified: 2014-08-04 17:11 UTC (History)
2 users (show)

See Also:
Kernel Version: 3.12
Subsystem:
Regression: No
Bisected commit-id:

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Description haarp 2014-08-02 17:37:04 UTC 
Hello,

I've recently been battling a performance regression on my Wifi, until I figured out that it was a driver issue. To be precise, it's a regression introduced by this commit:

iwlwifi: disable TX AMPDU by default for iwldvm, 205e2210daa975d92ace485a65a31ccc4077fe1a

Predictably, setting 11n_disable=8 restores performance. Without it, my throughput falls by almost an order of magnitude to 802.11g levels!

This can't be intended. Even as a trade-off for increased stability (which is what I understand this commit is for), this seems like a bad default.

Additionally, it's very hard to diagnose (took me many hours).

Can there be a better way?
Comment 1 Emmanuel Grumbach 2014-08-04 17:11:45 UTC 
I can't see another way.
I can't really debug the FW issues and most people care more for reliability than performance.
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