Re: [Qemu-devel] [PATCH 2/2] raw-posix: add Linux native AIO support

[Avi Kivity <avi@redhat.com>]

On 08/21/2009 05:48 PM, Christoph Hellwig wrote:
> On Fri, Aug 21, 2009 at 12:53:49PM +0300, Avi Kivity wrote:
>    
>>> + * Queue size (per-device).
>>> + *
>>> + * XXX: eventually we need to communicate this to the guest and/or make it
>>> + *      tunable by the guest.  If we get more outstanding requests at a
>>> time
>>> + *      than this we will get EAGAIN from io_submit which is communicated
>>> to
>>> + *      the guest as an I/O error.
>>> + */
>>> +#define MAX_EVENTS 128
>>>
>>>        
>> Or, we could queue any extra requests.
>>      
> That doesn't make much sense.    We'd just do an additional level of
> queueing in addition to those already optimized implementation in the
> guest and host kernels.  This is really just an issue of communicating
> the limits we have and deal with it efficiently.  It should be a
> relatively small add-on patch.
>    

You're right, virtio and scsi already know their queue sizes, should be 
easy to pass it down the stack.


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