Re: [Qemu-devel] unix sockets for qemu

[clownix]

Thank you for everything.

> On Tue, Feb 26, 2013 at 05:31:04PM +0100, Stefan Hajnoczi wrote:
>> On Mon, Feb 25, 2013 at 07:02:30PM -0600, address@hidden wrote:
>> > The associated file contains a README that will guide you through the
>> > experiment that shows the difference between unix socket carried
>> pings:
>> > 0.7ms and inet carried pings: 40ms!!!
>>
>> There is no fundamental reason for inet sockets to have a 40 millisecond
>> round-trip time on localhost.  I remember from years ago that Solaris
>> "fuses" localhost inet sockets and bypasses TCP for them.
>>
>> Adding a call to socket_set_nodelay() net/socket.c might help.
>
> I sent a patch to add socket_set_nodelay() to net/socket.c.
>
> Note that even before my patch I get sub-millisecond ping times on
> localhost with this:
>
>   $ qemu -netdev socket,listen=:1234,id=socket0 \
>          -device virtio-net-pci,netdev=socket0
>   $ qemu -netdev socket,connect=:1234,id=socket0 \
>          -device virtio-net-pci,netdev=socket0
>
> If you are seeing 40 ms average RTT on localhost then it's a
> configuration issue or bug in the test program you provided.
>
> Stefan
>