[TEST/REVIEW] cpu time accounting patch, step 2

[Andrew Gallatin]

Robert Watson writes:
 > 
 > On Fri, 10 Feb 2006, Andrew Gallatin wrote:
 > 
 > > Unfortunately, even after your patch, we are still about 38% slower than 
 > > linux x86_64 on the same box for loopback ping-pong, and 32% slower for 
 > > ping-pong over 10GbE.  (bandwidth is lower for streaming tests, and CPU 
 > > utilization is much, much much higher in FreeBSD as well).
 > >
 > > I think you nailed the biggest source of overhead, but there is apparently a 
 > > lot more performance that we can get out of the hardware. I'd love to see 
 > > you commit this.
 > 
 > I can't remember if I pointed you at this before, but I remember us talking 
 > about it by e-mail.  What happens to your loopback performance if you compile 
 > PREEMPTION out of the kernel?

As long as I have machdep.cpu_idle_hlt=0 and am using the BSD
scheduler, disabling preemption does not help.   If I do disable
preemption, then I can also enable machdep.cpu_idle_hlt without a
penalty.

Drew