linux-kernel - Re: [PATCH 1/3] printk: Release console_sem after logbuf

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Date:	Thu, 23 Jun 2011 19:03:28 +0000
From:	Pavel Machek <pavel@....cz>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, efault@....de,
	Arne Jansen <lists@...-jansens.de>,
	PaulMundt <lethal@...ux-sh.org>, linux-fbdev@...r.kernel.org
Subject: Re: [PATCH 1/3] printk: Release console_sem after logbuf_lock

vvOn Fri 2011-06-10 14:30:30, Peter Zijlstra wrote:
>On Fri, 2011-06-10 at 13:28 +0200, Peter Zijlstra wrote:
> > On Thu, 2011-06-09 at 16:57 -0700, Hugh Dickins wrote:
> > > 
> > > All console-related activity curently happens under spin_lock_irqsave(&console_lock). 
> > > This causes interrutps to be blocked for 1-2 milliseconds with vgacon, and for
> > > hundreds of milliseconds with fbdevs.  This results in network overruns, audio
> > > dropouts, dropped characters on serial ports and other such nice things.
> > 
> > Hmm, with these proposed patches we're actually back to that. I wonder
> > if fbdev is still that crappy..
> 
> So I tried adding a fbcon to my test box (not that it actually has a
> display, but who cares) and disabled lockdep (otherwise that's all I can
> catch on the latency tracer) to see if I could see whopping horrid
> latencies there, but I'm afraid I either failed to set things up
> properly or my fbcon isn't sucky enough.
> 
> What I did was enable:
> 
> CONFIG_FB=y
> CONFIG_FB_SIS=y
> CONFIG_FB_SIS_315=y (the board has XGI z7)

sis will be accelerated. Try vesafb; scrolling should be horrible.
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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