cvs commit: src/sys/i386/i386 local_apic.c

[John Baldwin]

On Wednesday 02 March 2005 09:17 am, John Baldwin wrote:
> jhb         2005-03-02 14:17:43 UTC
>
>   FreeBSD src repository
>
>   Modified files:
>     sys/i386/i386        local_apic.c
>   Log:
>   Tweak the lapic timer code to get the performance closer to the pre-lapic
>   timer case:
>   - Remove the virtual fooclock interrupt counters as they have served
> their purpose.
>   - Adjust the dividers for the different clock such that profhz is now a
>     multiple of stathz as in the non-lapic case, and the timer now runs at
>     hz * 2 rather than hz * 3.  With the new divisors, the default clock
>     rates are:
>
>     kern.clockrate: { hz = 1000, tick = 1000, profhz = 666, stathz = 133 }

With these changes and the 8254 interrupt turned off completely, I actually 
seem to get slightly better performance than pre-lapic timer, though ministat 
says that pre-lapic timer, the code with this change, and this change + 8254 
interrupt are all relatively the same with 95% confidence.  Before this 
change I was seeing about a 0.3% performance regression with lapic timer with 
95% confidence.

Also, it now should be obvious that profiling is patently evil. :)

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org