On 10/27/2010 07:41 PM, Gleb Natapov wrote:
> On Wed, Oct 27, 2010 at 05:09:41PM +0800, Xiao Guangrong wrote:
>> The async_pf number is very few since only pending interrupt can
>> let it re-enter to the guest mode.
>>
>> During my test(Host 4 CPU + 4G, Guest 4 VCPU + 6G), it's no
>> more than 10 requests in the system.
>>
>> So, we can only increase the completion counter in the work queue
>> context, and walk vcpu->async_pf.queue list to get all completed
>> async_pf
>>
> That depends on the load. I used memory cgroups to create very big
> memory pressure and I saw hundreds of apfs per second. We shouldn't
> optimize for very low numbers. With vcpu->async_pf.queue having more
> then one element I am not sure your patch is beneficial.
>
Maybe we need a new no-lock way to record the complete apfs, i'll reproduce
your test environment and improve it.
>> +
>> + list_del(&work->queue);
>> + vcpu->async_pf.queued--;
>> + kmem_cache_free(async_pf_cache, work);
>> + if (atomic_dec_and_test(&vcpu->async_pf.done))
>> + break;
> You should do atomic_dec() and always break. We cannot inject two apfs during
> one vcpu entry.
>
Sorry, i'm little confused.
Why 'atomic_dec_and_test(&vcpu->async_pf.done)' always break? async_pf.done is used to
record the complete apfs and many apfs may be completed when vcpu enters guest mode(it
means vcpu->async_pf.done > 1)
Look at the current code:
void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
{
......
spin_lock(&vcpu->async_pf.lock);
work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link);
list_del(&work->link);
spin_unlock(&vcpu->async_pf.lock);
......
}
You only handle one complete apf, why we inject them at once? I missed something? :-(
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
