NetworkingTodo

This page should cover all networking related activity in KVM, currently most info is related to virtio-net.

Stabilization is highest priority currently. DOA test matrix (all combinations should work):

       vhost: test both on and off, obviously
       test: hotplug/unplug, vlan/mac filtering, netperf,
            file copy both ways: scp, NFS, NTFS
       guests: linux: release and debug kernels, windows
       conditions: plain run, run while under migration,
               vhost on/off migration
       networking setup: simple, qos with cgroups
       host configuration: host-guest, external-guest

vhost-net driver projects

• iovec length limitations

• mergeable buffers: fix host->guest BW regression

• scalability tuning: figure out the best threading model to use

qemu projects

• fix hotplug issues

• migration with multiple macs/vlans

       qemu only sends ping with the first mac/no vlan:
        need to send it for all macs/vlan

virtio projects

• suspend/resume support
• API extension: improve small packet/large buffer performance:

 support "reposting" buffers for mergeable buffers,
 support pool for indirect buffers

• ring redesign:

     find a way to test raw ring performance 
     fix cacheline bounces 
     reduce interrupts
 Developer: Michael
      see patchset: virtio: put last seen used index into ring itself

=== projects involing other kernel components and/or networking stack

=

• rx mac filtering in tun

       the need for this is still not understood as we have filtering in bridge
       we have a small table of addresses, need to make it larger
       if we only need filtering for unicast (multicast is handled by IMP filtering)

• vlan filtering in tun

       the need for this is still not understood as we have filtering in bridge
       for small # if vlans we can use BPF

• zero copy tx/rx for macvtap

• multiqueue (involves all of vhost, qemu, virtio, networking stack)
• kvm MSI interrupt injection fast path

• kvm eventfd support for injecting level interrupts

• DMA emgine (IOAT) use in tun

• allow handling short packets from softirq context

• irq affinity:

 networking goes much faster with irq pinning:
 both with and without numa.
 what can be done to make the non-pinned setup go faster?

testing projects

• Cover test matrix with autotest
• Test with windows drivers, pass WHQL

== Short term plans

• multiqueue Krishna Jumar
• tx zero copy Shirley Ma
• rx zero copy Xin Xiaohui

== non-virtio-net devices e1000: bug in dealing with short frames (affect sun guests)

== bugzilla entries

should be fixed upstream (must verify): https://bugzilla.redhat.com/show_bug.cgi?id=623552 https://bugzilla.redhat.com/show_bug.cgi?id=632747 https://bugzilla.redhat.com/show_bug.cgi?id=632745

known minor bug in qemu: https://bugzilla.redhat.com/show_bug.cgi?id=581750

need to fix (mst is working on it): https://bugzilla.redhat.com/show_bug.cgi?id=623735

feature request (multiqueue): https://bugzilla.redhat.com/show_bug.cgi?id=632751

e1000 bug: https://bugzilla.redhat.com/show_bug.cgi?id=602205

== abandoned projects:

• Add GSO/checksum offload support to AF_PACKET(raw) sockets.

 status: incomplete

• guest kernel 2.6.31 seems to work well. Under certain workloads,

 virtio performance has regressed with guest kernels 2.6.32 and up
 (but still better than userspace). A patch has been posted:
 http://www.spinics.net/lists/netdev/msg115292.html
 status: might be fixed, need to test