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:

quoted

On Thu, 2011-06-09 at 16:57 -0700, Hugh Dickins wrote:

quoted

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.
-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html