Re: Re: [PATCH] virtio: Use ioeventfd for virtqueue notify

Avi Kivity
2010-10-04T08:04:29Z

On 10/04/2010 03:18 AM, Anthony Liguori wrote:
> On 10/03/2010 09:28 AM, Michael S. Tsirkin wrote:
>>
>>> This is using eventfd as well.
>> Sorry, I meant irqfd.
>
> I've tried using irqfd in userspace. It hurts performance quite a bit
> compared to doing an ioctl so I would suspect this too.
>
> A last_used_idx or similar mechanism should help performance quite a
> bit on top of ioeventfd too.
>

Any idea why? While irqfd does quite a bit of extra locking, it
shouldn't be that bad.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.