ACPI/power implementation causing performance loss with i7/Nehalem turbo boost

[Alexander Motin]

Kevin Day wrote:
> On Mar 6, 2010, at 12:05 AM, Daniel O'Connor wrote:
> Yeah, sorry for not mentioning that I had tried this and didn't see any change, so I thought I was on the wrong track.
> 
> # sysctl hw.acpi.cpu.cx_lowest=C3
> hw.acpi.cpu.cx_lowest: C1 -> C3
> 
> but it doesn't look like it's ever leaving C1:
> 
> hw.acpi.cpu.cx_lowest: C3
> dev.cpu.0.cx_supported: C1/3 C2/205 C3/245
> dev.cpu.0.cx_lowest: C3
> dev.cpu.0.cx_usage: 100.00% 0.00% 0.00% last 500us

You have too high interrupt rate for the C-states entering latencies
reported by your ACPI. You should significantly reduce number of
interrupts per core. For example, by setting:
kern.hz=100
hint.apic.0.clock=0
hint.atrtc.0.clock=0

-- 
Alexander Motin