Re: [Qemu-devel] VSOCK benchmark and optimizations

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Tue, Apr 02, 2019 at 09:37:06AM +0200, Stefano Garzarella wrote:
> On Tue, Apr 02, 2019 at 04:19:25AM +0000, Alex Bennée wrote:
> > 
> > Stefano Garzarella <sgarzare@redhat.com> writes:
> > 
> > > Hi Alex,
> > > I'm sending you some benchmarks and information about VSOCK CCing qemu-devel
> > > and linux-netdev (maybe this info could be useful for others :))
> > >
> > > One of the VSOCK advantages is the simple configuration: you don't need to set
> > > up IP addresses for guest/host, and it can be used with the standard POSIX
> > > socket API. [1]
> > >
> > > I'm currently working on it, so the "optimized" values are still work in
> > > progress and I'll send the patches upstream (Linux) as soon as possible.
> > > (I hope in 1 or 2 weeks)
> > >
> > > Optimizations:
> > > + reducing the number of credit update packets
> > >   - RX side sent, on every packet received, an empty packet only to inform the
> > >     TX side about the space in the RX buffer.
> > > + increase RX buffers size to 64 KB (from 4 KB)
> > > + merge packets to fill RX buffers
> > >
> > > As benchmark tool I used iperf3 [2] modified with VSOCK support:
> > >
> > >              host -> guest [Gbps]      guest -> host [Gbps]
> > > pkt_size    before opt.  optimized    before opt.  optimized
> > >   1K            0.5         1.6           1.4         1.4
> > >   2K            1.1         3.1           2.3         2.5
> > >   4K            2.0         5.6           4.2         4.4
> > >   8K            3.2        10.2           7.2         7.5
> > >   16K           6.4        14.2           9.4        11.3
> > >   32K           9.8        18.9           9.2        17.8
> > >   64K          13.8        22.9           8.8        25.0
> > >   128K         17.6        24.5           7.7        25.7
> > >   256K         19.0        24.8           8.1        25.6
> > >   512K         20.8        25.1           8.1        25.4
> > >
> > >
> > > How to reproduce:
> > >
> > > host$ modprobe vhost_vsock
> > > host$ qemu-system-x86_64 ... -device vhost-vsock-pci,guest-cid=3
> > >       # Note: Guest CID should be >= 3
> > >       # (0, 1 are reserved and 2 identify the host)
> > >
> > > guest$ iperf3 --vsock -s
> > >
> > > host$ iperf3 --vsock -c 3 -l ${pkt_size}      # host -> guest
> > > host$ iperf3 --vsock -c 3 -l ${pkt_size} -R   # guest -> host
> > >
> > >
> > > If you want, I can do a similar benchmark (with iperf3) using a networking
> > > card (do you have a specific configuration?).
> > 
> > My main interest is how it stacks up against:
> > 
> >   --device virtio-net-pci and I guess the vhost equivalent
> 
> I'll do some tests with virtio-net and vhost.
> 
> > 
> > AIUI one of the motivators was being able to run something like NFS for
> > a guest FS over vsock instead of the overhead from UDP and having to
> > deal with the additional complication of having a working network setup.
> > 
> 
> CCing Stefan.
> 
> I know he is working on virtio-fs that maybe suite better with your use cases.
> He also worked on VSOCK support for NFS, but I think it is not merged upstream.

Hi Alex,
David Gilbert, Vivek Goyal, Miklos Szeredi, and I are working on
virtio-fs for host<->guest file sharing.  It performs better than
virtio-9p and we're currently working on getting it upstream (first the
VIRTIO device spec, then Linux and QEMU patches).

You can read about it and try it here:

https://virtio-fs.gitlab.io/

Stefan

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