SCHED_4BSD bad interactivity on 7.0 vs 6.3

[Stefan Sperling]

On Sun, Jul 13, 2008 at 01:34:11AM -0700, Nate Eldredge wrote:
> On Sun, 13 Jul 2008, Kris Kennaway wrote:
> 
> > Nate Eldredge wrote:
> >> I wrote a small program which forks two processes that run gettimeofday() 
> >> in a tight loop to see how long they get scheduled out.  On 6.3 the maximum 
> >> latency is usually under 100 ms.  On 7.0 it is 500 ms or more even when 
> >> nothing else is running on the system.  When a compile is also running it 
> >> is sometimes 1400 ms or more.
> 
> This test shows a difference even in single user mode, when X is not 
> running at all.

I was seeing similar problems (audio stutter during compiles, jerky
mouse) after upgrading to 7.0. The box is an Athlon-XP 2400+ with
1GB of RAM.

Since removing SMP support from the kernel and switching to ULE,
interactivity has been acceptible again. I did not update the
xserver at the time, and I can't recall if it has been updated
since.

Stefan
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