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

16 Jul 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.

Lee