[linux-audio-user] Re: [a-users] Re: [a-devel] File system and Voluntary Kernel Preemption

Lee Revell rlrevell at joe-job.com
Fri Jul 16 15:24:23 EDT 2004

On Fri, 2004-07-16 at 04:33, Malcolm Baldridge wrote:
> >  Some of these fixes were to
> > extremely important areas (get_user_pages, a fix for
> > framebuffer-scrolling issue, and more). 
> It goes against common sense (to anyone with kernel knowledge) to use the
> console framebuffer anyway.
> The duration of kernel locks and the CPU expense of blowing bitmaps around
> like that are shocking.
> Seriously.  Use text-mode consoles, or a native AGP-driver a la nvidia, ati,
> or whatever.  But using a "stupid" framebuffer driver is asking for hardcore
> latency blow-outs.

I am using text-mode consoles, and switching back and forth between
those and X using ctrl-alt-F[1-7].  I sent Andrew Morton some XRUN
traces and he said one of them was caused by framebuffer scolling inside
lock_kernel(), and the fix was to remove (un)lock_kernel() from
do_tty_write().  This particular fix may not be in -mm1, because he
seemed to think it would cause problems (display corruption, etc).  It
has not caused any problems for me.

Maybe I am confused about the 'framebuffer' vs. a text-mode console, I
thought they were the same.  Anyway, the point is, switching from X to a
text-mode console and back caused XRUNS before, and now it doesn't.


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