[mac80211 ] Wifi Network slownes bisected

[mac80211 ] Wifi Network slownes bisected

[Alejandro Riveira Fernández]

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 I have a rt2500pci card

 I noticed that my wifi connection has slowed when stitching
from 2.6.29.1 to 2.6.29.4 (it is also slow on 30-rc6)
Also 2.6.27 (ubuntu) does not suffer it.

 I bisected and came to the following commit as the culprit

 I can test patches and if you need more info just ask.

$ git bisect good
64e1b00c974ddeae6a60ebb02e1c487371905cea is first bad commit
commit 64e1b00c974ddeae6a60ebb02e1c487371905cea
Author: Johannes Berg <johannes@sipsolutions.net>
Date:   Fri Apr 24 16:05:16 2009 +0000

    mac80211: fix basic rate bitmap calculation
    
    upstream commit: 7e0986c17f695952ce5d61ed793ce048ba90a661
    
    "mac80211: fix basic rates setting from association response"
    introduced a copy/paste error.
    
    Unfortunately, this not just leads to wrong data being passed
    to the driver but is remotely exploitable for some hardware or
    driver combinations.
    
    Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
    Signed-off-by: John W. Linville <linville@tuxdriver.com>
    Signed-off-by: Chris Wright <chrisw@sous-sol.org>

:040000 040000 e9e479210b46ae45f9c84badd57039df44d4077c
ea0b719e549849446e62e065b2570fab5a801895 M      net

 Bisect Log
$ git bisect log
git bisect start
# bad: [186f9b18b94afd0b75a8ec1b394b0f119d479eb6] Linux 2.6.29.4
git bisect bad 186f9b18b94afd0b75a8ec1b394b0f119d479eb6
# good: [8e0ee43bc2c3e19db56a4adaa9a9b04ce885cd84] Linux 2.6.29
git bisect good 8e0ee43bc2c3e19db56a4adaa9a9b04ce885cd84
# good: [fda28853bc4bc053ef2fafb5c7d2a26e6ce4b4bf] KVM: Fix missing smp tlb flush in invlpg
git bisect good fda28853bc4bc053ef2fafb5c7d2a26e6ce4b4bf
# bad: [7843dcfe1115e9412e6e83492e17f9c75b5a062d] mv643xx_eth: OOM handling fixes
git bisect bad 7843dcfe1115e9412e6e83492e17f9c75b5a062d
# bad: [87b59eac0914ab407df57fe23d880dccd9a9436d] virtio-rng: Remove false BUG for spurious callbacks
git bisect bad 87b59eac0914ab407df57fe23d880dccd9a9436d
# good: [24016c735e651f179692432f18176348caeb82b0] scsi: mpt: suppress debugobjects warning
git bisect good 24016c735e651f179692432f18176348caeb82b0
# good: [5c47524b514b5bb3732c3b893338a210d67da3cd] thinkpad-acpi: fix LED blinking through timer trigger
git bisect good 5c47524b514b5bb3732c3b893338a210d67da3cd
# bad: [d595990048ad17ba7b0ad50438ed64f88b7c25ca] KVM: MMU: disable global page optimization
git bisect bad d595990048ad17ba7b0ad50438ed64f88b7c25ca
# bad: [64e1b00c974ddeae6a60ebb02e1c487371905cea] mac80211: fix basic rate bitmap calculation
git bisect bad 64e1b00c974ddeae6a60ebb02e1c487371905cea
# good: [d2d83e1f527b6b0faf15d54b22c032ed5812d054] ALSA: us122l: add snd_us122l_free()
git bisect good d2d83e1f527b6b0faf15d54b22c032ed5812d054

 



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Re: [mac80211 ] Wifi Network slownes bisected

[Johannes Berg]

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On Thu, 2009-05-21 at 17:38 +0200, Alejandro Riveira Fernández wrote:

>  I noticed that my wifi connection has slowed when stitching
> from 2.6.29.1 to 2.6.29.4 (it is also slow on 30-rc6)
> Also 2.6.27 (ubuntu) does not suffer it.

> $ git bisect good
> 64e1b00c974ddeae6a60ebb02e1c487371905cea is first bad commit
> commit 64e1b00c974ddeae6a60ebb02e1c487371905cea
> Author: Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
> Date:   Fri Apr 24 16:05:16 2009 +0000
> 
>     mac80211: fix basic rate bitmap calculation

Well ... How much did your connection slow down? It is clear that this
commit might possibly slow down your connection, but not by a lot. And
that's only because before we were sending with a higher rate than the
AP allowed us to... If you need the higher speed then set your AP to
G-only to make it include more rates in the basic rate set, that'll
speed up your connection properly.

That's all discounting driver bugs which may exist, of course.

johannes

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Re: [mac80211 ] Wifi Network slownes bisected

[Alejandro Riveira Fernández]

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El Thu, 21 May 2009 18:08:11 +0200
Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org> escribió:

> On Thu, 2009-05-21 at 17:38 +0200, Alejandro Riveira Fernández wrote:
> 
> >  I noticed that my wifi connection has slowed when stitching
> > from 2.6.29.1 to 2.6.29.4 (it is also slow on 30-rc6)
> > Also 2.6.27 (ubuntu) does not suffer it.
> 
> > $ git bisect good
> > 64e1b00c974ddeae6a60ebb02e1c487371905cea is first bad commit
> > commit 64e1b00c974ddeae6a60ebb02e1c487371905cea
> > Author: Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
> > Date:   Fri Apr 24 16:05:16 2009 +0000
> > 
> >     mac80211: fix basic rate bitmap calculation
> 
> Well ... How much did your connection slow down? 

  Enough to notice it when connecting through a 3MBit
 Adsl connection i.e. with the patch i get 30 40 60 ...
 80 kiB maximum without it full 310 KiB so it is an issue
 for me (i have inet <-> modem-router <-> myPC only so i can
 not test with another pc)
 

> It is clear that this
> commit might possibly slow down your connection, but not by a lot.

 Well it does by a lot avg of 60 KiB vs 300 KiB is lot for me

 And that's only because before we were sending with a higher rate than the
> AP allowed us to... If you need the higher speed then set your AP to
> G-only to make it include more rates in the basic rate set, that'll
> speed up your connection properly.

 My Ap is set to "mixed" but i connect at G speeds ie iwconfig show 54M or 48M
 or 36M but the connection is slow nonetheless 
 Do you think that would make such a difference (the ap mode)?

 Also with the patch i notice weird bumps on connection rates and without it
 the connection "feels" more stable
 
 > 
> That's all discounting driver bugs which may exist, of course.

 well i bisected and the problem is with this commit. Could be
 that rt2x00 is doing something wrong with that "rate bitmap" ??
 I'm not programmer so i can not check myself

> 
> johannes

Alejandro

  Thanks for the response...


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