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

[Blue S. <bla...@gm...>]

On 4/17/08, Anthony Liguori <ali...@us...> 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.

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.