Re: [Xen-devel] lock in vhpet

[Keir Fraser <keir@xxxxxxx>]

On 19/04/2012 09:27, "Tim Deegan" <tim@xxxxxxx> wrote:

> At 05:19 +0000 on 19 Apr (1334812779), Zhang, Yang Z wrote:
>> There have no problem with this patch, it works well. But it cannot
>> fix the win8 issue. It seems there has some other issues with hpet. I
>> will look into it.  Thanks for your quick patch.
> 
> The lock in hvm_get_guest_time() will still be serializing the hpet
> reads.  But since it needs to update a shared variable, that will need to
> haul cachelines around anyway.

Yes, that's true. You could try the attached hacky patch out of interest, to
see what that lock is costing you in your scenario. But if we want
consistent monotonically-increasing guest time, I suspect we can't get rid
of the lock, so that's going to limit our scalability unavoidably. Shame.

 -- Keir

> Tim.
>

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