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    SubjectRe: [PATCHv2 0/2] vhost: a kernel-level virtio server
    On Wed, Aug 12, 2009 at 07:56:05AM -0400, Gregory Haskins wrote:
    > Michael S. Tsirkin wrote:
    > > On Tue, Aug 11, 2009 at 07:49:37PM -0400, Gregory Haskins wrote:
    > >> Michael S. Tsirkin wrote:
    > >>> This implements vhost: a kernel-level backend for virtio,
    > >>> The main motivation for this work is to reduce virtualization
    > >>> overhead for virtio by removing system calls on data path,
    > >>> without guest changes. For virtio-net, this removes up to
    > >>> 4 system calls per packet: vm exit for kick, reentry for kick,
    > >>> iothread wakeup for packet, interrupt injection for packet.
    > >>>
    > >>> Some more detailed description attached to the patch itself.
    > >>>
    > >>> The patches are against 2.6.31-rc4. I'd like them to go into linux-next
    > >>> and down the road 2.6.32 if possible. Please comment.
    > >> I will add this series to my benchmark run in the next day or so. Any
    > >> specific instructions on how to set it up and run?
    > >>
    > >> Regards,
    > >> -Greg
    > >>
    > >
    > > 1. use a dedicated network interface with SRIOV, program mac to match
    > > that of guest (for testing, you can set promisc mode, but that is
    > > bad for performance)
    >
    > Are you saying SRIOV is a requirement, and I can either program the
    > SRIOV adapter with a mac or use promis? Or are you saying I can use
    > SRIOV+programmed mac OR a regular nic + promisc (with a perf penalty).

    SRIOV is not a requirement. And you can also use a dedicated
    nic+programmed mac if you are so inclined.

    > > 2. disable tso,gso,lro with ethtool
    >
    > Out of curiosity, wouldnt you only need to disable LRO on the adapter,
    > since the other two (IIUC) are transmit path and are therefore
    > influenced by the skb's you generate in vhost?

    Hmm, makes sense. I'll check this and let you know.

    >
    > > 3. add vhost=ethX
    >
    > You mean via "ip link" I assume?

    No, that's a new flag for virtio in qemu:

    -net nic,model=virtio,vhost=veth0

    > Regards,
    > -Greg
    >




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