Re: [Xen-devel] cpuidle causing Dom0 soft lockups

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 08/02/2010 09:08, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>> - Use per-CPU vcpu list to iterate the VCPU, which is more scalable. The
>> original scheduler does not provide such kind of list, so this patch
>> implement the list in scheduler code.
> 
> I'm still not really happy with that solution. I'd rather say that e.g.
> vcpu_sleep_nosync() should set a flag in the vcpu structure indicating
> whether that one is "urgent", and the scheduler should just maintain
> a counter of "urgent" vCPU-s per pCPU. Setting the flag when a vCPU
> is put to sleep guarantees that it won't be mis-treated if it got woken
> by the time acpi_processor_idle() looks at it (or at least the window
> would be minimal - not sure if it can be eliminated completely). Plus
> not having to traverse a list is certainly better for scalability, not the
> least since you're traversing a list (necessarily) including sleeping
> vCPU-s (i.e. the ones that shouldn't affect the performance/
> responsiveness of the system).
> 
> But in the end it would certainly depend much more on Keir's view on
> it than on mine...

Your suggestion makes sense to me.

 K.



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