Re: add back pending timer irqs for kernel APIC timer

Avi Kivity
2007-08-13T13:36:43Z

Dong, Eddie wrote:
>> Note that my old lapic branch did a similar "tdf" thing as well and it
>> worked quite nicely, so I think Eddie is on the right track with
>> adding this.
>>
>
> I just copied the whole APIC timer stuff from your old patch at that
> time as TODO. maybe I missed something :-(
>
> Time virtualization has quit a long way to go and it is quit very
> beginning now. Something in my plan:
>
> 1: Current 3 patches to fix the pending irq issues and accumulate issue.
>
> 2: stop hrtimer when the guest is descheduled to increase scalibility
> and remove apic->lock.
>

Why is this important? An hrtimer is just an entry on a list, no?

Do you mean, just if the guest is preempted (not during hlt)? Is it so
important? We're talking a few thousand wakeups per second.

> 3: Use scale + shift like Xen did to make sure no internal overflow if
> we run guest contiguously for long time say 2 years.
>

hrtimers are in 64-bit nanoseconds. That gives about 160 years.

> Above 1-3 is already in Xen and we just need to port.
>
>
> 4: Should we use hrtimer? How efficieny it is?
>
>
>

Sure, hrtimer is the future.

> Will u be able to help together?
> thx,eddie
>

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