Re: [Xen-ia64-devel] RFC: ptc.ga implementation for SMP-g

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Le Mardi 04 Avril 2006 17:12, Xu, Anthony a écrit :
> From: Tristan Gingold [mailto:Tristan.Gingold@xxxxxxxx]
>
> >Sent: 2006?4?4? 23:03
> >
> >> Yes, resetting the rid impacts the performance, that makes IPI method
> >> worse. I have an idea about handling ptc.ga. But I am not sure whether
> >> it is feasible.
> >>
> >> The control flow is as below
> >> 1. vcpu1 emulates ptc.ga
> >> 2. vcpu1 executes vhpt_flush_address to purge current LP VHPT,
> >>   and executes ptc.l to purge machine TLB on current LPs.
> >> 3. vcpu1 creates a structure which describe this ptc.ga, including
> >> virtual address, address range and rid, and connect this structure to
> >> vcpu2. 4. then vcpu1 sets a flag in vcpu2, indicating there is ptc.ga
> >> executed on this VMM.
> >> 5. When vcpu2 traps into hypervisor, hypervisor will check whether this
> >>   flag is set, if yes, vcpu2 will execute vhpt_flush_address and ptc.l.
> >
> >  6. vcpu1 waits for vcpu2 until it has done the job.
> >
> >> There is a time window between purges of vcpu1 and vcpu2, I'm not sure
> >> whether it is workable.
> >
> >The IPI could makes vcpu2 entering into the hypervisor faster.
>
> Yes, but IPI will cause extra save/restore on other vcpus.
Right.
> And as you said IPI may cause trouble when considering migration.
> If above method is feasible, I prefer this one.
How to be sure the time window is not too long ?
vcpu1 must waits for vcpu2.

Tristan.



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