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oasisbob
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PostPosted: Mon Nov 29, 2004 12:21 am    Post subject: Airport performance in Linux Reply with quote

I have a G3 iBook 700mhz which has been running linux for a week or so now. Everything is working great, but I've noticed a big performance problem with using the built in Airport for Wifi in Linux as compared to OS X.

For testing, I'm connecting to an open, unencrypted access point at home. I'm using kernel-2.6.9-gentoo-r2 with airport support compiled as a module.

Everything "works" in gentoo, but webpage loading often stalls out. It's hard to describe how horrible it is -- it's far worse than a 56k modem. However, the pages will sometimes load eventually -- if you let them.

Anyone had this problem before?
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porodzila
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PostPosted: Mon Nov 29, 2004 2:21 am    Post subject: Reply with quote

I think you must have some other problem than Linux making your card slow
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stimuli
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PostPosted: Mon Nov 29, 2004 2:39 am    Post subject: Reply with quote

Such as your ISP, or more specifically, their DNS's periodically flaking out. There's a host of free software to speed up your linux box. I use PDNSD and Privoxy to great effect.
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oasisbob
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PostPosted: Mon Nov 29, 2004 10:14 am    Post subject: Reply with quote

I'm almost positive that it's not an ISP issue. Promise. I see the problem on other access points as well (one with access to a full 45mbit bandwidth, and I'm on the team that administers the DNS server), and the I only see the problem in Linux. Never in OS X.

It's really frustrating -- but I have no idea what to look into next. Can any of the iw* utilites provide statistics that could help track this down? I'm tempted to just tcpdump the connection for a while and see if I can figure out exactly where the delay is occuring.

I agree that this might not be a WiFi problem per se, but I'm not sure what else it would be. I'm sure that it's a "linux" (or any other app associated with it) problem, and that makes me sad.
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zojas
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PostPosted: Wed Dec 01, 2004 5:39 pm    Post subject: Reply with quote

bizarre. I don't have my ibook with me right now, but I also own a 700MHz G3 ibook with gentoo. I've never noticed the airport being slower than in OS X. I was thinking at some point I had done some timing with rsync, and the bandwidth came out about the same. I'll have to do some timings tonight to verify.

I can say that the time it takes to ssh in to another machine on my network from my ibook in linux via airport is breathtakingly FASTER than in OS X. I tend to stay booted in either OS X or linux for a week or so at a time, and I ssh in to my mail server A LOT in both OSes. when I reboot from OS X to linux and ssh for the first time, it's a quite noticable speed improvement to get the remote prompt.

anyway, my gut feeling is that you have something misconfigured somewhere; don't know if it's in gentoo on your ibook, or elsewhere on your network. once I do some timings, we should compare what kind of speeds we can each get.
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zojas
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PostPosted: Thu Dec 02, 2004 5:35 am    Post subject: Reply with quote

I did some timings. I looked in my ~/tmp folder (which is where I store junk that I'll probably be interested in for about 3 minutes and then will never look at again) and 'ls -lShr' told me the biggest file in there was a 19mb wav file (the gentoo song, normalized version).

so I transferred the file back and forth a few times using rsync over airport, without the -z flag (so rsync didn't try to compress the data).

I uploaded the file twice and downloaded the file twice in both OSes.

OS X got the exact same upload speed as gentoo.

gentoo was slightly faster at downloading.

for upload in OS X, I got:

Code:

wrote 19102658 bytes  read 40 bytes  570229.79 bytes/sec
total size is 19100204  speedup is 1.00
wrote 19102658 bytes  read 40 bytes  587775.32 bytes/sec
total size is 19100204  speedup is 1.00


for upload in gentoo, I got:

Code:

wrote 19102658 bytes  read 40 bytes  587775.32 bytes/sec
total size is 19100204  speedup is 1.00
wrote 19102658 bytes  read 40 bytes  587775.32 bytes/sec
total size is 19100204  speedup is 1.00


for download in OS X, I got:

Code:

wrote 36 bytes  read 19102662 bytes  471671.56 bytes/sec
total size is 19100204  speedup is 1.00
wrote 36 bytes  read 19102662 bytes  496173.64 bytes/sec
total size is 19100204  speedup is 1.00


for download in gentoo, I got:

Code:

wrote 36 bytes  read 19102662 bytes  570229.79 bytes/sec
total size is 19100204  speedup is 1.00
wrote 36 bytes  read 19102662 bytes  570229.43 bytes/sec
total size is 19100204  speedup is 1.00


so, taking the fastest time for each os, and operation, and converting to megabits/sec (multiply by 8, divide by 1024 twice), and rounding to 8 significant digits:

Code:

gentoo:
upload: 4.4843698 download: 4.3505080
OS X:     
upload: 4.4843698 download: 3.7855045

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heavyt
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PostPosted: Thu Dec 02, 2004 7:29 pm    Post subject: Reply with quote

Thanks for the nice bit of work Zojas. :)
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zojas
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PostPosted: Thu Dec 02, 2004 8:58 pm    Post subject: Reply with quote

you're welcome. it made me curious to see if I was getting the throughput I thought I was.
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oasisbob
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PostPosted: Fri Dec 03, 2004 6:58 am    Post subject: Reply with quote

hey thanks zojas. I can't say it helped any, but your numbers are interesting.

I'm still baffled by the problem, but oh well. I'm starting to think about other possibilities which could be causing problems.

Anyone know of good "so you want convienent, secure, wireless?" type howtos? I use 3-4 different access points a day (home, office, campus), and manually restarting init files is making me think that there's gotta be a better way.

Thanks everyone who'is helping me with this (and other) question(s). I really appreciate the help and discussion.
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zojas
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PostPosted: Fri Dec 03, 2004 2:30 pm    Post subject: Reply with quote

I have several different locations set up using gentoo's virtual run levels and some perl scripts. there is a doc somewhere on the gentoo page about virtual runlevels. also, I have the scripts I use at the link in my sig. my kernel config is there too.

there are a couple of programs talked about here on the forums for handling multiple locations too. quickswitch is one of them, I think there is at least one other program too.
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stimuli
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PostPosted: Fri Dec 03, 2004 5:18 pm    Post subject: Reply with quote

Theres a wireless roaming daemon as well, I forget what it's called.
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