Re: [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler

[Christian Borntraeger]

On 11/07/12 13:51, Raghavendra K T wrote:
>>>> Almost all s390 kernels use diag9c (directed yield to a given guest cpu) for spinlocks, though.
>>>
>>> Perhaps x86 should copy this.
>>
>> See arch/s390/lib/spinlock.c
>> The basic idea is using several heuristics:
>> - loop for a given amount of loops
>> - check if the lock holder is currently scheduled by the hypervisor
>>    (smp_vcpu_scheduled, which uses the sigp sense running instruction)
>>    Dont know if such thing is available for x86. It must be a lot cheaper
>>    than a guest exit to be useful
> 
> Unfortunately we do not have information on lock-holder.

That would be an independent patch and requires guest changes.


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