Re: DragonFly-2.3.0.864.gc5b83 master sys/platform/pc32/apic mpapic.c sys/platform/pc32/isa clock.c sys/platform/pc64/isa clock.c sys/platform/vkernel/platform systimer.c sys/sys systimer.h

[Sepherosa Ziehau <sepherosa@xxxxxxxxx>]

On Tue, May 5, 2009 at 8:37 PM, Sepherosa Ziehau <sepherosa@gmail.com> wrote:
> On Tue, May 5, 2009 at 2:07 AM, Hasso Tepper <hasso@estpak.ee> wrote:
>> Matthew Dillon wrote:
>>>     450 interrupts/sec sounds ok for an idle system.  I'd expect a
>>> higher number, actually.
>>
>> Yes, but ...
>>
>>>     I wonder if the load calculations are being messed up by the C3
>>>     state.  The code path for the per-cpu hardclock interrupt has
>>> always been fairly sensitive.  With the 8254 it was being driven by
>>> IPIs. Now it is being driven by an actual interrupt so there might be
>>> an issue with how it distinguishes the system state when accounting for
>>> the clock tick.
>>
>> It seems to be a real load though - applications lag etc.
>>
>> And one more thing. With sephe's change it's even worse _without_ lapic.
>> The interrupt load is still there and the rate of clock interrupts
>> doubles to ~800.
>
> My git repo on leaf, lapic_timer branch, see whether it helps.

If it does not improve things, I intend to use cputimer_intr_switch()
in the related sysctl, if C3 state is configured as cx_lowest.

Best Regards,
sephe

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