linux-kernel - Unusually low speeds with ath5k and iwl3945

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Message-ID: <492719ED.5000006@gmail.com>
Date:	Fri, 21 Nov 2008 22:28:29 +0200
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Bob Copeland <me@...copeland.com>
CC:	ipw3945-devel@...ts.sourceforge.net, ath5k-devel@...ts.ath5k.org,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	wally@...blackmoor.net
Subject: Unusually low speeds with ath5k and iwl3945

Hi,

sorry for cross-posting, but this issue really spans both iwl3945 and ath5k.

I have two laptops (acer 5720, and aspire one) and I see some strange speed issues.

I initially blamed iwl3945, then thought it got fixed, but now I have ath5k, and speeds are low
and I suspect that both drivers has bugs regarding to speed.

Walter Francis, once reported similar issue, so I cc'ed him too.
He says that 2.6.25 works fine for iwl3945.
I'll test this, and bisect if necessary. 

So here it goes:

System setup:

a wired desktop connected to a router, I call it just router
as wired connection there is 100 Mbits/s and this can't
be the bottleneck.

two laptops, both are close to the router, signal strength is -50 dBm on laptop
and -55 dBm on aspire one (they are really close, they are on same desktop).
Also I did try to bring both laptops to router, and this really didn't help much.

Only one of laptops was on when I did speed tests between a laptop and router.

I did those tests several times, and interleaved them in different order.

For data transfers, contents of /dev/zero were send to /dev/null via TCP connection,
using netcat.

So here are the speeds:

router->iwl3945 = 2.3 Mbytes/s, solid speed, never dropped much, was consistent across tests.

iwl3945->router	= 1.0 Mbytes/s max, on first test, it dropped often to 300 Kbytes/s

Then in another test for whole session it stayed at 200 Kbytes/s, it was same upload speed
to ath5k too, the speed varied a lot too.

router->ath5k   = 1.4 Mbytes/s max, was pretty solid, also noticed that
iwconfig shows maximum 18M, although my router supports all B/G speeds.
attempts to set higher speed resulted in full connection loss.
also association was dropping often, and that resulted in few minutes of no transfer
at all.

ath5k->router	= 1.4 Mbytes/s max, also the same 18 Mbytes/s issue , 
and same association issue.

And now for the worst part:

ath5k->iwl3945  = 800 Kbytes/s, but speed very often dropped to 600 Kbytes/s, and once it did drop to around 80~100 Kbytes/s
I did see same association drops, but they were rare. 

iwl3945->ath5k  = 500 Kbytes/s  and often drops to 300 Mbytes/s.

Best regards,
	Maxim Levitsky
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