linux-kernel - Re: b44: regression in 2.6.22 (resend)

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Message-Id: <200705282255.56490.maxi@daemonizer.de>
Date:	Mon, 28 May 2007 22:55:46 +0200
From:	Maximilian Engelhardt <maxi@...monizer.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Michael Buesch <mb@...sch.de>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Jeff Garzik <jgarzik@...ox.com>,
	Gary Zambrano <zambrano@...adcom.com>, netdev@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: b44: regression in 2.6.22 (resend)

On Monday 28 May 2007, Thomas Gleixner wrote:
> On Mon, 2007-05-28 at 19:44 +0200, Maximilian Engelhardt wrote:
> > > Can you please keep CONFIG_HIGH_RES_TIMERS and CONFIG_NOHZ and try the
> > > following combinations on the kernel command line:
> > >
> > > 1) highres=off nohz=off (should be the same as your working config)
> > > 2) highres=off
> > > 3) nohz=off
> >
> > I tested this with my 2.6.22-rc3 kernel, here are the results:
> >
> > without any special boot parameters: problem does appear
> > highres=off nohz=off: problem does not appear
> > highres=off: problem does not appear
> > nohz=off: problem does appear
>
> Is there any other strange behavior of the high res enabled kernel than
> the b44 problem ?

I didn't notice anything.

>
> > I additionally built my 2.6.22-rc2-mm1 kernel without High Resolution
> > Timer, but the high ping problem is still there.
>
> Hmm, that's mysterious. Wild guess is that highres exposes the hidden
> "feature" in a different way than rc2-mm1 does.

I think the bug in 2.6.21/22-rc3 is a different one that the one in 
2.6.22-rc2-mm1, but that's also only a wild guess :)

I'll explain this a bit:
In 2.6.21/22-rc3 is the same b44 driver that has been in the stock kernels for 
some time. With this driver and High Resolution Timer turned on I get 
problems using iperf. The problems are that the systems becomes really slow 
and unresponsive.  Michael Buesch thought this could be an IRQ storm which 
sounds logical to me. This bug did never happen to me before I startet the 
iperf test.

The other issue happens only with 2.6.22-rc2-mm1 which includes the b44 ssb 
spilt. It's independed wether High Resolution Timer is turned on or off I 
always get very varying and high ping times. The iperf-test doesn't show the 
problems from 2.6.21/22-rc3.

Maxi

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