Re: [kvm-devel] [Qemu-devel] [PATCH 1/5] PCI DMA API (v3)

[Anthony Liguori <anthony@codemonkey.ws>]

Blue Swirl wrote:
> On 4/17/08, Anthony Liguori <aliguori@us.ibm.com> wrote:
>   
>>  Yes, the vector version of packet receive is tough.  I'll take a look at
>> your patch.  Basically, you need to associate a set of RX vectors with each
>> VLANClientState and then when it comes time to deliver a packet to the VLAN,
>> before calling fd_read, see if there is an RX vector available for the
>> client.
>>
>>  In the case of tap, I want to optimize further and do the initial readv()
>> to one of the clients RX buffers and then copy that RX buffer to the rest of
>> the clients if necessary.
>>     
>
> The vector versions should also help SLIRP to add IP and Ethernet
> headers to the incoming packets.
>   

Yeah, I'm hoping that with my posted linux-aio interface, I can add 
vector support since linux-aio has a proper asynchronous vector function.

Are we happy with the DMA API?  If so, we should commit it now so we can 
start adding proper vector interfaces for net/block.

Regards,

Anthony Liguori

> I made an initial version of the vectored AIO SCSI with ESP. It does
> not work, but I can see that just using the vectors won't give too
> much extra performance, because at least initially the vector length
> is 1. Collecting the statuses may be tricky.
>   
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