machdep.cpu_idle_hlt and SMP perf?

[Ivan Voras]

Andrew Gallatin wrote:
> Why dooes machdep.cpu_idle_hlt=1 drop my 10GbE network rx
> performance by a considerable amount (7.5Gbs -> 5.5Gbs)?

For what it's worth, here are results of unixbench's "context1" 
benchmark on an old P3 SMP with and without cpu_idle_hlt (6-stable):


x hlt=0
+ hlt=1
+--------------------------------------------------------------------------+
| +     ++   +                    +                   x  xx  x            x|
||_______M___A____________|                          |____M__A_______|     |
+--------------------------------------------------------------------------+
     N           Min           Max        Median           Avg        Stddev
x   5        346203        355234        347787      349229.8     3549.1559
+   5        322710        337269        325631      327663.8     5622.9044
Difference at 95.0% confidence
	-21566 +/- 6857.28
	-6.1753% +/- 1.96354%
	(Student's t, pooled s = 4701.78)