iwl3945 slow for downloading

iwl3945 slow for downloading

[Cédric Auger]

hello
i've a problem for iwl3945 and didn't find on google something about
that. i have the kernel 2.6.26 and use the kernel's driver. when i was
with the ipw3945, i could download with a speed of at least 600k/s, and
sometimes more.
it's some time i changed for iwl3945 and didn't see some difference
exept it works better in several ways, but some times ago, i noticed
that dowloading big images was slow.
i checked to transfer a file between 2 computer by wifi, and the
download is limited to about 130-140k/s. when i plug a cable, i go
directly to 900kb/s.
i tried to remove all debugging options in the kernel for that driver,
but no differences.
i don't see any difference when i go on website, it's only the max
download speed wich cannot go more thant 130kb/s.
i have a dell m1710, with intel 3945ABG
my lspci :
0c:00.0 Network controller: Intel Corporation PRO/Wireless 3945ABG
Network Connection (rev 02)
i'm on debian sid, with a 2.6.26 kernel and use wpa supplicant
i have networkmanager as daemon, but use /etc/network/interfaces and
ifup to manage my wifi
i have no error on my syslog, daemon.log, wpa_supplicant log,
i don't know if you need some extra informations about my system.
thanks
cedric

Re: iwl3945 slow for downloading

[Felix Fietkau]

C=E9dric Auger wrote:
> hello
> i've a problem for iwl3945 and didn't find on google something about
> that. i have the kernel 2.6.26 and use the kernel's driver. when i wa=
s
> with the ipw3945, i could download with a speed of at least 600k/s, a=
nd
> sometimes more.
> it's some time i changed for iwl3945 and didn't see some difference
> exept it works better in several ways, but some times ago, i noticed
> that dowloading big images was slow.
> i checked to transfer a file between 2 computer by wifi, and the
> download is limited to about 130-140k/s. when i plug a cable, i go
> directly to 900kb/s.
I don't know if it helps with debugging this issue, but I've seen the s=
ame
on a laptop from a friend of mine (same card).

After some searching I found that setting the AP to g-only mode instead=
 of
b+g mixed made it work at decent speeds. Another symptom of this slowdo=
wn is
that there is typically an unnaturally high number of retransmissions o=
n the
air, which eats up a lot of airtime.

I've spent some time looking through the code to find the reason for th=
is
but couldn't find anything yet (maybe somebody from Intel could help).

- Felix

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Re: iwl3945 slow for downloading

[Larry Finger]

Felix Fietkau wrote:
> I don't know if it helps with debugging this issue, but I've seen the same
> on a laptop from a friend of mine (same card).
> 
> After some searching I found that setting the AP to g-only mode instead of
> b+g mixed made it work at decent speeds. Another symptom of this slowdown is
> that there is typically an unnaturally high number of retransmissions on the
> air, which eats up a lot of airtime.
> 
> I've spent some time looking through the code to find the reason for this
> but couldn't find anything yet (maybe somebody from Intel could help).

Just for comparison, my BCM4312 running b43 from the latest wireless-testing 
gets the following tcpperf throughput:

AP Mode          TX          RX

Mixed b/g    19.8 MB/s   23.0 MB/s
g-only       20.5 MB/s   23.1 MB/s

For these tests, the connecting end was wired to the router. The difference in 
TX speeds was about what I expected - the small difference in RX speeds was not. 
In any case, if you see a large difference with iwl3945, that would be useful 
information.

You can obtain tcpperf from http://wand.cs.waikato.ac.nz/~stj2/nsc/software.html

Larry

Re: iwl3945 slow for downloading

[Cédric Auger]

Le Sat, 26 Jul 2008 10:54:41 -0500,
Larry Finger <Larry.Finger@lwfinger.net> a =C3=A9crit :

> Felix Fietkau wrote:
> > I don't know if it helps with debugging this issue, but I've seen
> > the same on a laptop from a friend of mine (same card).
> >=20
> > After some searching I found that setting the AP to g-only mode
> > instead of b+g mixed made it work at decent speeds. Another symptom
> > of this slowdown is that there is typically an unnaturally high
> > number of retransmissions on the air, which eats up a lot of
> > airtime.
> >=20
> > I've spent some time looking through the code to find the reason
> > for this but couldn't find anything yet (maybe somebody from Intel
> > could help).
>=20
> Just for comparison, my BCM4312 running b43 from the latest
> wireless-testing gets the following tcpperf throughput:
>=20
> AP Mode          TX          RX
>=20
> Mixed b/g    19.8 MB/s   23.0 MB/s
> g-only       20.5 MB/s   23.1 MB/s
>=20
> For these tests, the connecting end was wired to the router. The
> difference in TX speeds was about what I expected - the small
> difference in RX speeds was not. In any case, if you see a large
> difference with iwl3945, that would be useful information.
>=20
> You can obtain tcpperf from
> http://wand.cs.waikato.ac.nz/~stj2/nsc/software.html

hello
thanks for your answers.
i tried to set my ap to g-only, but i cannot :-( the wifi box is given
by my provider and it seems cannot be changed...
so i tried tcpperf, this is the result :

cedric:/home/grisbi/tcpperf-1.754# ./tcpperf -c 192.168.0.4 -t 30
Duration: 30 9482usec
Bytes sent: 5481472 (5353 kB 5 MB 0 GB)
Bandwidth: 1461264 b/s (1461.26 kb/s 1.46 Mb/s)
Close duration: 0s 22usec

then i tried to download an image of ubuntu and i had about 900kb/s,
so very good and i don't understand...  then i tried to send a big file
with scp to the other computer, as user and as root, it begins at
2,2MB/s and decrease untill 150kb/s and stays between 130-200kb/s
i did again a tcpperf with -t 300 to check if it's not with the time,
but i have 1,30MB/s, seems correct.

second test :
i stop the wifi and plug a cable. the second computer is still in wifi.
tcpperf gives me 17Mb/s and the same file with scp is sent with about
2,2MB/s...
so now i really don't understand, from internet, loading work untill
900kb/s (ok for me), but beween 2 computers on my network i have max
200kb/s...
hopes this can be usefull
thanks
cedric



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Re: iwl3945 slow for downloading

[Felix Fietkau]

Larry Finger wrote:
> Just for comparison, my BCM4312 running b43 from the latest wireless-testing 
> gets the following tcpperf throughput:
> 
> AP Mode          TX          RX
> 
> Mixed b/g    19.8 MB/s   23.0 MB/s
> g-only       20.5 MB/s   23.1 MB/s
> 
> For these tests, the connecting end was wired to the router. The difference in 
> TX speeds was about what I expected - the small difference in RX speeds was not. 
> In any case, if you see a large difference with iwl3945, that would be useful 
> information.
On the laptop that I mentioned, this problem was only happening sometimes.
I did not figure out what actually triggered it.
Most of the time the throughput was similar to what you posted here,
but when it went down, it went down right to 100-120 KB/s

Could it be that this is triggered by the use b/g protection mode due to reception
of foreign beacons of B devices by the AP? Has anybody tested RTS/CTS in detail?

- Felix

Re: iwl3945 slow for downloading

[Larry Finger]

C=C3=A9dric Auger wrote:
> Le Sat, 26 Jul 2008 10:54:41 -0500,
> Larry Finger <Larry.Finger@lwfinger.net> a =C3=A9crit :
>=20
>> Felix Fietkau wrote:
>>> I don't know if it helps with debugging this issue, but I've seen
>>> the same on a laptop from a friend of mine (same card).
>>>
>>> After some searching I found that setting the AP to g-only mode
>>> instead of b+g mixed made it work at decent speeds. Another symptom
>>> of this slowdown is that there is typically an unnaturally high
>>> number of retransmissions on the air, which eats up a lot of
>>> airtime.
>>>
>>> I've spent some time looking through the code to find the reason
>>> for this but couldn't find anything yet (maybe somebody from Intel
>>> could help).
>> Just for comparison, my BCM4312 running b43 from the latest
>> wireless-testing gets the following tcpperf throughput:
>>
>> AP Mode          TX          RX
>>
>> Mixed b/g    19.8 MB/s   23.0 MB/s
>> g-only       20.5 MB/s   23.1 MB/s
>>
>> For these tests, the connecting end was wired to the router. The
>> difference in TX speeds was about what I expected - the small
>> difference in RX speeds was not. In any case, if you see a large
>> difference with iwl3945, that would be useful information.
>>
>> You can obtain tcpperf from
>> http://wand.cs.waikato.ac.nz/~stj2/nsc/software.html
>=20
> hello
> thanks for your answers.
> i tried to set my ap to g-only, but i cannot :-( the wifi box is give=
n
> by my provider and it seems cannot be changed...
> so i tried tcpperf, this is the result :
>=20
> cedric:/home/grisbi/tcpperf-1.754# ./tcpperf -c 192.168.0.4 -t 30
> Duration: 30 9482usec
> Bytes sent: 5481472 (5353 kB 5 MB 0 GB)
> Bandwidth: 1461264 b/s (1461.26 kb/s 1.46 Mb/s)
> Close duration: 0s 22usec
>=20
> then i tried to download an image of ubuntu and i had about 900kb/s,
> so very good and i don't understand...  then i tried to send a big fi=
le
> with scp to the other computer, as user and as root, it begins at
> 2,2MB/s and decrease untill 150kb/s and stays between 130-200kb/s
> i did again a tcpperf with -t 300 to check if it's not with the time,
> but i have 1,30MB/s, seems correct.
>=20
> second test :
> i stop the wifi and plug a cable. the second computer is still in wif=
i.
> tcpperf gives me 17Mb/s and the same file with scp is sent with about
> 2,2MB/s...
> so now i really don't understand, from internet, loading work untill
> 900kb/s (ok for me), but beween 2 computers on my network i have max
> 200kb/s...
> hopes this can be usefull

It looks as if your receive rate is a lot higher than the transmit rate=
=2E You can=20
check that by using the computer with the iwl3945 as the server and ini=
tiate=20
tcpperf from the other end.

Larry
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Re: iwl3945 slow for downloading

[Cédric Auger]

Le Sat, 26 Jul 2008 16:10:59 -0500,
Larry Finger <Larry.Finger@lwfinger.net> a =C3=A9crit :

> C=C3=A9dric Auger wrote:
> > Le Sat, 26 Jul 2008 10:54:41 -0500,
> > Larry Finger <Larry.Finger@lwfinger.net> a =C3=A9crit :
> >=20
> >> Felix Fietkau wrote:
> >>> I don't know if it helps with debugging this issue, but I've seen
> >>> the same on a laptop from a friend of mine (same card).
> >>>
> >>> After some searching I found that setting the AP to g-only mode
> >>> instead of b+g mixed made it work at decent speeds. Another
> >>> symptom of this slowdown is that there is typically an
> >>> unnaturally high number of retransmissions on the air, which eats
> >>> up a lot of airtime.
> >>>
> >>> I've spent some time looking through the code to find the reason
> >>> for this but couldn't find anything yet (maybe somebody from Inte=
l
> >>> could help).
> >> Just for comparison, my BCM4312 running b43 from the latest
> >> wireless-testing gets the following tcpperf throughput:
> >>
> >> AP Mode          TX          RX
> >>
> >> Mixed b/g    19.8 MB/s   23.0 MB/s
> >> g-only       20.5 MB/s   23.1 MB/s
> >>
> >> For these tests, the connecting end was wired to the router. The
> >> difference in TX speeds was about what I expected - the small
> >> difference in RX speeds was not. In any case, if you see a large
> >> difference with iwl3945, that would be useful information.
> >>
> >> You can obtain tcpperf from
> >> http://wand.cs.waikato.ac.nz/~stj2/nsc/software.html
> >=20
> > hello
> > thanks for your answers.
> > i tried to set my ap to g-only, but i cannot :-( the wifi box is
> > given by my provider and it seems cannot be changed...
> > so i tried tcpperf, this is the result :
> >=20
> > cedric:/home/grisbi/tcpperf-1.754# ./tcpperf -c 192.168.0.4 -t 30
> > Duration: 30 9482usec
> > Bytes sent: 5481472 (5353 kB 5 MB 0 GB)
> > Bandwidth: 1461264 b/s (1461.26 kb/s 1.46 Mb/s)
> > Close duration: 0s 22usec
> >=20
> > then i tried to download an image of ubuntu and i had about 900kb/s=
,
> > so very good and i don't understand...  then i tried to send a big
> > file with scp to the other computer, as user and as root, it begins
> > at 2,2MB/s and decrease untill 150kb/s and stays between 130-200kb/=
s
> > i did again a tcpperf with -t 300 to check if it's not with the
> > time, but i have 1,30MB/s, seems correct.
> >=20
> > second test :
> > i stop the wifi and plug a cable. the second computer is still in
> > wifi. tcpperf gives me 17Mb/s and the same file with scp is sent
> > with about 2,2MB/s...
> > so now i really don't understand, from internet, loading work until=
l
> > 900kb/s (ok for me), but beween 2 computers on my network i have ma=
x
> > 200kb/s...
> > hopes this can be usefull
>=20
> It looks as if your receive rate is a lot higher than the transmit
> rate. You can check that by using the computer with the iwl3945 as
> the server and initiate tcpperf from the other end.

hi
i didn't think about that...=20
i did the test and i have a bandwidth of 7,55Mb/s... more than for the
other test...
so i did a transfer by scp from the other computer to my computer,
begin to 2,2Mb/s and decrease to 930kb/s, which is good for me.
so if i resume :

my computer 1 to computer 2 : 100-200kb/s
computer 2 to computer 1 : 950kb/s
internet to computer 1 : 950kb/s

then download seems correct, but upload seems bad. but if we look the
results of tcpperf :
computer 1 to computer 2 : 1,5Mb/s
computer 2 to computer 1 : 7,5Mb/s

perhaps 1,5Mb/s for upload is not good as i thought ?
thanks
cedric
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Re: iwl3945 slow for downloading

[Cédric Auger]

Le Sat, 26 Jul 2008 18:56:22 +0200,
=46elix Fietkau <nbd@openwrt.org> a =C3=A9crit :

> Larry Finger wrote:
> > Just for comparison, my BCM4312 running b43 from the latest
> > wireless-testing gets the following tcpperf throughput:
> >=20
> > AP Mode          TX          RX
> >=20
> > Mixed b/g    19.8 MB/s   23.0 MB/s
> > g-only       20.5 MB/s   23.1 MB/s
> >=20
> > For these tests, the connecting end was wired to the router. The
> > difference in TX speeds was about what I expected - the small
> > difference in RX speeds was not. In any case, if you see a large
> > difference with iwl3945, that would be useful information.

> On the laptop that I mentioned, this problem was only happening
> sometimes. I did not figure out what actually triggered it.
> Most of the time the throughput was similar to what you posted here,
> but when it went down, it went down right to 100-120 KB/s

i'm happy that it happened sometimes too because i was begining to feel
crazy ;-) all the last tests seem to show an upload problem, but at the
begining, i was thinking i had a download problem (from internet), but
from yesterday, i cannot reproduce that, only upload...
=20
> Could it be that this is triggered by the use b/g protection mode due
> to reception of foreign beacons of B devices by the AP? Has anybody
> tested RTS/CTS in detail?

for that i think it goes beyond my abilities...
i forgot to say about the AP, i think it's not g wifi, it's MIMO.
perhaps it could change something.
and for information, the second computer i use to do the tests is also
a 3945ABG intel wireless, but installed with ubuntu and iwl3945 too
(but the default installation), with a 2.6.24 kernel.
the difference with me, except the computer itself, is debian, kernel
2.6.26 compiled by myself, and before i used ipw3945, but remove it
completely
thanks
cedric
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Re: iwl3945 slow for downloading

[Stefan Monnier]

>>>>> "C=E9dric" =3D=3D C=E9dric Auger <cedric@grisbi.org>

Is it just me, or is this thread terribly confusing in terms of
bits-vs-bytes?  Please try and be careful not to confuse the two, and
ideally follow the convention that "b=3Dbits" and "B=3Dbytes",
"Mb=3Dmegabits", "MB=3Dmegabytes", ...


        Stefan

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Re: iwl3945 slow for downloading

[Larry Finger]

Stefan Monnier wrote:
>>>>>> "C=E9dric" =3D=3D C=E9dric Auger <cedric@grisbi.org>
>=20
> Is it just me, or is this thread terribly confusing in terms of
> bits-vs-bytes?  Please try and be careful not to confuse the two, and
> ideally follow the convention that "b=3Dbits" and "B=3Dbytes",
> "Mb=3Dmegabits", "MB=3Dmegabytes", ...

I was very careful in my postings. Every number that I quoted was in Mb=
/s, i.e.=20
Mega bits per second.

Larry
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