From KVM
Line 7: Line 7:
  
 
* virtio 1.0 support for linux guests
 
* virtio 1.0 support for linux guests
    required for maintainatibility
+
        required for maintainatibility
    mid.gmane.org/1414081380-14623-1-git-send-email-mst@redhat.com
+
        mid.gmane.org/1414081380-14623-1-git-send-email-mst@redhat.com
    Developer: MST,Cornelia Huck
+
        Developer: MST,Cornelia Huck
  
 
* virtio 1.0 support in qemu
 
* virtio 1.0 support in qemu
    required for maintainatibility
+
        required for maintainatibility
    mid.gmane.org/20141024103839.7162b93f.cornelia.huck@de.ibm.com
+
        mid.gmane.org/20141024103839.7162b93f.cornelia.huck@de.ibm.com
    Developer: Cornelia Huck, MST
+
        Developer: Cornelia Huck, MST
  
 
* improve net polling for cpu overcommit
 
* improve net polling for cpu overcommit
    exit busy loop when another process is runnable
+
        exit busy loop when another process is runnable
    mid.gmane.org/20140822073653.GA7372@gmail.com
+
        mid.gmane.org/20140822073653.GA7372@gmail.com
    mid.gmane.org/1408608310-13579-2-git-send-email-jasowang@redhat.com
+
        mid.gmane.org/1408608310-13579-2-git-send-email-jasowang@redhat.com
    Another idea is make the busy_read/busy_poll dynamic like dynamic PLE window.
+
        Another idea is make the busy_read/busy_poll dynamic like dynamic PLE window.
    Developer: Jason Wang, MST
+
        Developer: Jason Wang, MST
  
 
* vhost-net/tun/macvtap cross endian support
 
* vhost-net/tun/macvtap cross endian support
    mid.gmane.org/1414572130-17014-2-git-send-email-clg@fr.ibm.com
+
        mid.gmane.org/1414572130-17014-2-git-send-email-clg@fr.ibm.com
    Developer: Cédric Le Goater, MST
+
        Developer: Cédric Le Goater, MST
  
 
* BQL/aggregation for virtio net
 
* BQL/aggregation for virtio net
  dependencies: orphan packets less agressively, enable tx interrupt  
+
        dependencies: orphan packets less agressively, enable tx interrupt  
  Developers: MST, Jason
+
        Developers: MST, Jason
 +
 
 
* orphan packets less agressively (was make pktgen works for virtio-net ( or partially orphan ))
 
* orphan packets less agressively (was make pktgen works for virtio-net ( or partially orphan ))
 
       virtio-net orphans all skbs during tx, this used to be optimal.
 
       virtio-net orphans all skbs during tx, this used to be optimal.
Line 46: Line 47:
  
 
* enable tx interrupt (conditionally?)
 
* enable tx interrupt (conditionally?)
  Small packet TCP stream performance is not good. This is because virtio-net orphan the packet during ndo_start_xmit() which disable the TCP small packet optimizations like TCP small Queue and AutoCork. The idea is enable the tx interrupt to TCP small packets.
+
      Small packet TCP stream performance is not good. This is because
  Jason's idea: switch between poll and tx interrupt mode based on recent statistics.
+
      virtio-net orphan the packet during ndo_start_xmit() which disable the  
  MST's idea: use a per descriptor flag for virtio to force interrupt for a specific packet.
+
      TCP small packet optimizations like TCP small Queue and AutoCork. The
  Developer: Jason Wang, MST
+
      idea is enable the tx interrupt to TCP small packets.
 +
      Jason's idea: switch between poll and tx interrupt mode based on recent statistics.
 +
      MST's idea: use a per descriptor flag for virtio to force interrupt for a specific packet.
 +
      Developer: Jason Wang, MST
 
   
 
   
 
 
 
* vhost-net polling
 
* vhost-net polling
      mid.gmane.org/20141029123831.A80F338002D@moren.haifa.ibm.com
+
      mid.gmane.org/20141029123831.A80F338002D@moren.haifa.ibm.com
      Developer: Razya Ladelsky
+
      Developer: Razya Ladelsky
 
+
  
 
* support more queues in tun
 
* support more queues in tun
    We limit TUN to 8 queues, but we really want
+
      We limit TUN to 8 queues, but we really want 1 queue per guest CPU. The
    1 queue per guest CPU. The limit comes from net
+
      limit comes from net core, need to teach it to allocate array of
    core, need to teach it to allocate array of
+
      pointers and not array of queues. Jason has an draft patch to use flex
    pointers and not array of queues.
+
      array. Another thing is to move the flow caches out of tun_struct.
    Jason has an draft patch to use flex array.
+
      http://mid.gmane.org/1408369040-1216-1-git-send-email-pagupta@redhat.com
    Another thing is to move the flow caches out of tun_struct.
+
      Developers: Pankaj Gupta, Jason Wang
    http://mid.gmane.org/1408369040-1216-1-git-send-email-pagupta@redhat.com
+
    Developers: Pankaj Gupta, Jason Wang
+
  
 
* enable multiqueue by default
 
* enable multiqueue by default
Line 85: Line 84:
 
       Developer: Jason Wang
 
       Developer: Jason Wang
 
        
 
        
 
 
* bridge without promisc/allmulti mode in NIC
 
* bridge without promisc/allmulti mode in NIC
  given hardware support, teach bridge
+
      given hardware support, teach bridge to program mac/vlan filtering in NIC
  to program mac/vlan filtering in NIC
+
      Helps performance and security on noisy LANs
  Helps performance and security on noisy LANs
+
      http://comments.gmane.org/gmane.linux.network/266546
  http://comments.gmane.org/gmane.linux.network/266546
+
      Done for unicast, but not for multicast.
  Done for unicast, but not for multicast.
+
      Developer: Vlad Yasevich
  Developer: Vlad Yasevich
+
  
 
* Improve stats, make them more helpful for per analysis
 
* Improve stats, make them more helpful for per analysis
  Developer: Sriram Narasimhan?
+
      Developer: Sriram Narasimhan?
  
 
* Enable LRO with bridging
 
* Enable LRO with bridging
  Enable GRO for packets coming to bridge from a tap interface
+
      Enable GRO for packets coming to bridge from a tap interface
  Better support for windows LRO
+
      Better support for windows LRO
  Extend virtio-header with statistics for GRO packets:
+
      Extend virtio-header with statistics for GRO packets:
  number of packets coalesced and number of duplicate ACKs coalesced
+
      number of packets coalesced and number of duplicate ACKs coalesced
  Developer: Dmitry Fleytman?
+
      Developer: Dmitry Fleytman?
  
 
* IPoIB infiniband bridging
 
* IPoIB infiniband bridging
  Plan: implement macvtap for ipoib and virtio-ipoib
+
      Plan: implement macvtap for ipoib and virtio-ipoib
  Developer: Marcel Apfelbaum
+
      Developer: Marcel Apfelbaum
 
+
 
+
  
 
* interrupt coalescing
 
* interrupt coalescing
  Reduce the number of interrupt
+
      Reduce the number of interrupt
  Rx interrupt coalescing should be good for rx stream throughput.
+
      Rx interrupt coalescing should be good for rx stream throughput.
  Tx interrupt coalescing will help the optimization of enabling tx interrupt conditionally.
+
      Tx interrupt coalescing will help the optimization of enabling tx
  Developer: Jason Wang
+
      interrupt conditionally.
 
+
      Developer: Jason Wang
 
+
  
 
* sharing config interrupts
 
* sharing config interrupts
  Support more devices by sharing a single msi vector
+
      Support more devices by sharing a single msi vector between multiple
  between multiple virtio devices.
+
      virtio devices.
  (Applies to virtio-blk too).
+
      (Applies to virtio-blk too).
  Developer: Amos Kong
+
      Developer: Amos Kong
 
+
  
 
* Multi-queue macvtap with real multiple queues
 
* Multi-queue macvtap with real multiple queues
        Macvtap only provides multiple queues to user in the form of multiple
+
      Macvtap only provides multiple queues to user in the form of multiple
        sockets.  As each socket will perform dev_queue_xmit() and we don't
+
      sockets.  As each socket will perform dev_queue_xmit() and we don't
        really have multiple real queues on the device, we now have a lock
+
      really have multiple real queues on the device, we now have a lock
        contention.  This contention needs to be addressed.
+
      contention.  This contention needs to be addressed.
        Developer: Vlad Yasevich
+
      Developer: Vlad Yasevich
  
 
* better xmit queueing for tun
 
* better xmit queueing for tun
        when guest is slower than host, tun drops packets
+
      when guest is slower than host, tun drops packets aggressively. This is
        aggressively. This is because keeping packets on
+
      because keeping packets on the internal queue does not work well.
        the internal queue does not work well.
+
      Re-enable functionality to stop queue, probably with some watchdog to
        re-enable functionality to stop queue,
+
      help with buggy guests.
        probably with some watchdog to help with buggy guests.
+
      Developer: MST
        Developer: MST
+
  
 
* Dev watchdog for virtio-net:
 
* Dev watchdog for virtio-net:
        Implement a watchdog for virtio-net. This will be useful for hunting host bugs early.
+
      Implement a watchdog for virtio-net. This will be useful for hunting host bugs early.
        Developer: Julio Faracco <jcfaracco@gmail.com>
+
      Developer: Julio Faracco <jcfaracco@gmail.com>
  
 +
* Extend virtio_net header for future offloads
 +
      virtio_net header is currently fixed sized and only supports
 +
      segmentation offloading.  It would be useful that would could
 +
      attach other data to virtio_net header to support things like
 +
      vlan acceleration, IPv6 fragment_id pass-through, rx and tx-hash
 +
      pass-through and some other ideas.
 +
      Developer: Vlad Yasevich <vyasevic@redhat.com>
  
 
=== projects in need of an owner ===
 
=== projects in need of an owner ===

Revision as of 12:41, 10 February 2015

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

TODO: add bugzilla entry links.

projects in progress. contributions are still very wellcome!

  • virtio 1.0 support for linux guests
       required for maintainatibility
       mid.gmane.org/1414081380-14623-1-git-send-email-mst@redhat.com
       Developer: MST,Cornelia Huck
  • virtio 1.0 support in qemu
       required for maintainatibility
       mid.gmane.org/20141024103839.7162b93f.cornelia.huck@de.ibm.com
       Developer: Cornelia Huck, MST
  • improve net polling for cpu overcommit
       exit busy loop when another process is runnable
       mid.gmane.org/20140822073653.GA7372@gmail.com
       mid.gmane.org/1408608310-13579-2-git-send-email-jasowang@redhat.com
       Another idea is make the busy_read/busy_poll dynamic like dynamic PLE  window.
       Developer: Jason Wang, MST
  • vhost-net/tun/macvtap cross endian support
       mid.gmane.org/1414572130-17014-2-git-send-email-clg@fr.ibm.com
       Developer: Cédric Le Goater, MST
  • BQL/aggregation for virtio net
       dependencies: orphan packets less agressively, enable tx interrupt 
       Developers: MST, Jason
  • orphan packets less agressively (was make pktgen works for virtio-net ( or partially orphan ))
      virtio-net orphans all skbs during tx, this used to be optimal.
      Recent changes in guest networking stack and hardware advances
      such as APICv changed optimal behaviour for drivers.
      We need to revisit optimizations such as orphaning all packets early
      to have optimal behaviour.
      this should also fix pktgen which is currently broken with virtio net:
      orphaning all skbs makes pktgen wait for ever to the refcnt.
      Jason's idea: bring back tx interrupt (partially)
      Jason's idea: introduce a flag to tell pktgen not for wait
      Discussion here: https://patchwork.kernel.org/patch/1800711/
      MST's idea: add a .ndo_tx_polling not only for pktgen
      Developers: Jason Wang, MST
  • enable tx interrupt (conditionally?)
      Small packet TCP stream performance is not good. This is because
      virtio-net orphan the packet during ndo_start_xmit() which disable the 
      TCP small packet optimizations like TCP small Queue and AutoCork. The
      idea is enable the tx interrupt to TCP small packets.
      Jason's idea: switch between poll and tx interrupt mode based on recent statistics.
      MST's idea: use a per descriptor flag for virtio to force interrupt for a specific packet.
      Developer: Jason Wang, MST

  • vhost-net polling
      mid.gmane.org/20141029123831.A80F338002D@moren.haifa.ibm.com
      Developer: Razya Ladelsky
  • support more queues in tun
      We limit TUN to 8 queues, but we really want 1 queue per guest CPU. The
      limit comes from net core, need to teach it to allocate array of
      pointers and not array of queues. Jason has an draft patch to use flex
      array.  Another thing is to move the flow caches out of tun_struct.
      http://mid.gmane.org/1408369040-1216-1-git-send-email-pagupta@redhat.com
      Developers: Pankaj Gupta, Jason Wang
  • enable multiqueue by default
      Multiqueue causes regression in some workloads, thus
      it is off by default. Documentation/networking/scaling.txt
      Detect and enable/disable
      automatically so we can make it on by default?
      depends on: BQL
      This is because GSO tends to batch less when mq is enabled.
      https://patchwork.kernel.org/patch/2235191/
      Developer: Jason Wang
  • rework on flow caches
      Current hlist implementation of flow caches has several limitations:
      1) at worst case, linear search will be bad
      2) not scale
      https://patchwork.kernel.org/patch/2025121/
      Developer: Jason Wang
      
  • bridge without promisc/allmulti mode in NIC
      given hardware support, teach bridge to program mac/vlan filtering in NIC
      Helps performance and security on noisy LANs
      http://comments.gmane.org/gmane.linux.network/266546
      Done for unicast, but not for multicast.
      Developer: Vlad Yasevich
  • Improve stats, make them more helpful for per analysis
      Developer: Sriram Narasimhan?
  • Enable LRO with bridging
      Enable GRO for packets coming to bridge from a tap interface
      Better support for windows LRO
      Extend virtio-header with statistics for GRO packets:
      number of packets coalesced and number of duplicate ACKs coalesced
      Developer: Dmitry Fleytman?
  • IPoIB infiniband bridging
      Plan: implement macvtap for ipoib and virtio-ipoib
      Developer: Marcel Apfelbaum
  • interrupt coalescing
      Reduce the number of interrupt
      Rx interrupt coalescing should be good for rx stream throughput.
      Tx interrupt coalescing will help the optimization of enabling tx
      interrupt conditionally.
      Developer: Jason Wang
  • sharing config interrupts
      Support more devices by sharing a single msi vector between multiple
      virtio devices.
      (Applies to virtio-blk too).
      Developer: Amos Kong
  • Multi-queue macvtap with real multiple queues
      Macvtap only provides multiple queues to user in the form of multiple
      sockets.  As each socket will perform dev_queue_xmit() and we don't
      really have multiple real queues on the device, we now have a lock
      contention.  This contention needs to be addressed.
      Developer: Vlad Yasevich
  • better xmit queueing for tun
      when guest is slower than host, tun drops packets aggressively. This is
      because keeping packets on the internal queue does not work well.
      Re-enable functionality to stop queue, probably with some watchdog to
      help with buggy guests.
      Developer: MST
  • Dev watchdog for virtio-net:
      Implement a watchdog for virtio-net. This will be useful for hunting host bugs early.
      Developer: Julio Faracco <jcfaracco@gmail.com>
  • Extend virtio_net header for future offloads
      virtio_net header is currently fixed sized and only supports
      segmentation offloading.  It would be useful that would could
      attach other data to virtio_net header to support things like
      vlan acceleration, IPv6 fragment_id pass-through, rx and tx-hash
      pass-through and some other ideas.
      Developer: Vlad Yasevich <vyasevic@redhat.com>

projects in need of an owner

  • improve netdev polling for virtio.
 There are two kinds of netdev polling:
 - netpoll - used for debugging
 - rx busy polling for virtio-net [DONE]
   see https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=91815639d8804d1eee7ce2e1f7f60b36771db2c9. 1 byte netperf TCP_RR shows 127% improvement.
   Future work is co-operate with host, and only does the busy polling when there's no other process in host cpu. 
 contact: Jason Wang
  • drop vhostforce
 it's an optimization, probbaly not worth it anymore
  • avoid userspace virtio-net when vhost is enabled.
 ATM we run in userspace until DRIVER_OK
 this doubles our security attack surface,
 so it's best avoided.
  • feature negotiation for dpdk/vhost user
 feature negotiation seems to be broken
  • switch dpdk to qemu vhost user
 this seems like a better interface than
  character device in userspace,
  designed for out of process networking
  • netmap - like approach to zero copy networking
  is anything like this feasible on linux?
  • vhost-user: clean up protocol
 address multiple issues in vhost user protocol:
  missing VHOST_NET_SET_BACKEND
  make more messages synchronous (with a reply)
  VHOST_SET_MEM_TABLE, VHOST_SET_VRING_CALL
   mid.gmane.org/541956B8.1070203@huawei.com
   mid.gmane.org/54192136.2010409@huawei.com
  Contact: MST
  • ethtool seftest support for virtio-net
       Implement selftest ethtool method for virtio-net for regression test e.g the CVEs found for tun/macvtap, qemu and vhost.
       http://mid.gmane.org/1409881866-14780-1-git-send-email-hjxiaohust@gmail.com
       Contact: Jason Wang
  • vhost-net scalability tuning: threading for many VMs
     Plan: switch to workqueue shared by many VMs
     http://www.mail-archive.com/kvm@vger.kernel.org/msg69868.html

http://domino.research.ibm.com/library/cyberdig.nsf/1e4115aea78b6e7c85256b360066f0d4/479e3578ed05bfac85257b4200427735!OpenDocument

     Contact: Razya Ladelsky, Bandan Das
     Testing: netperf guest to guest
  • DPDK with vhost-user
 Support vhost-user in addition to vhost net cuse device
 Contact: Linhaifeng, MST
  • DPDK with vhost-net/user: fix offloads
 DPDK requires disabling offloads ATM,
 need to fix this.
 Contact: MST
  • reduce per-device memory allocations
 vhost device is very large due to need to
 keep large arrays of iovecs around.
 we do need large arrays for correctness,
 but we could move them out of line,
 and add short inline arrays for typical use-cases.
 contact: MST
  • batch tx completions in vhost
 vhost already batches up to 64 tx completions for zero copy
 batch non zero copy as well
 contact: Jason Wang
  • better parallelize small queues
 don't wait for ring full to kick.
 add api to detect ring almost full (e.g. 3/4) and kick
 depends on: BQL
 contact: MST
  • improve vhost-user unit test
 support running on machines without hugetlbfs
 support running with more vm memory layouts
 Contact: MST
  • tun: fix RX livelock
       it's easy for guest to starve out host networking
       open way to fix this is to use napi 
       Contact: MST
  • large-order allocations
  see 28d6427109d13b0f447cba5761f88d3548e83605
  contact: MST
  • reduce networking latency:
 allow handling short packets from softirq or VCPU context
 Plan:
   We are going through the scheduler 3 times
   (could be up to 5 if softirqd is involved)
   Consider RX: host irq -> io thread -> VCPU thread ->
   guest irq -> guest thread.
   This adds a lot of latency.
   We can cut it by some 1.5x if we do a bit of work
   either in the VCPU or softirq context.
 Testing: netperf TCP RR - should be improved drastically
          netperf TCP STREAM guest to host - no regression
 Contact: MST
  • device failover to allow migration with assigned devices
 https://fedoraproject.org/wiki/Features/Virt_Device_Failover
 Contact: Gal Hammer, Cole Robinson, Laine Stump, MST
  • Reuse vringh code for better maintainability
 This project seems abandoned?
 Contact: Rusty Russell
  • use kvm eventfd support for injecting level-triggered interrupts
 aim: enable vhost by default for level interrupts.
 The benefit is security: we want to avoid using userspace
 virtio net so that vhost-net is always used.
 Alex emulated (post & re-enable) level-triggered interrupt in KVM for
 skipping userspace. VFIO already enjoied the performance benefit,
 let's do it for virtio-pci. Current virtio-pci devices still use
 level-interrupt in userspace.
 see: kernel:
 7a84428af [PATCH] KVM: Add resampling irqfds for level triggered interrupts
qemu:
 68919cac [PATCH] hw/vfio: set interrupts using pci irq wrappers
          (virtio-pci didn't use the wrappers)
 e1d1e586 [PATCH] vfio-pci: Add KVM INTx acceleration
 Contact: Amos Kong, MST       
  • Head of line blocking issue with zerocopy
      zerocopy has several defects that will cause head of line blocking problem:
      - limit the number of pending DMAs
      - complete in order
      This means is one of some of the DMAs were delayed, all other will also delayed. This could be reproduced with following case:
      - boot two VMS VM1(tap1) and VM2(tap2) on host1 (has eth0)
      - setup tbf to limit the tap2 bandwidth to 10Mbit/s
      - start two netperf instances one from VM1 to VM2, another from VM1 to an external host whose traffic go through eth0 on host
      Then you can see not only VM1 to VM2 is throttled, but also VM1 to external host were also throttled.
      For this issue, a solution is orphan the frags when en queuing to non work conserving qdisc.
      But we have have similar issues in other case:
      - The card has its own priority queues
      - Host has two interface, one is 1G another is 10G, so throttle 1G may lead traffic over 10G to be throttled.
      The final solution is to remove receive buffering at tun, and convert it to use NAPI
      Contact: Jason Wang, MST
      Reference: https://lkml.org/lkml/2014/1/17/105
  • network traffic throttling
 block implemented "continuous leaky bucket" for throttling
 we can use continuous leaky bucket to network
 IOPS/BPS * RX/TX/TOTAL
 Developer: Amos Kong
  • Allocate mac_table dynamically
 In the future, maybe we can allocate the mac_table dynamically instead
 of embed it in VirtIONet. Then we can just does a pointer swap and
 gfree() and can save a memcpy() here.
 Contact: Amos Kong
  • reduce conflict with VCPU thread
   if VCPU and networking run on same CPU,
   they conflict resulting in bad performance.
   Fix that, push vhost thread out to another CPU
   more aggressively.
   Contact: Amos Kong
  • 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)
       Contact: Amos Kong
  • vlan filtering in tun
       the need for this is still not understood as we have filtering in bridge
       Contact: Amos Kong


  • add documentation for macvlan and macvtap
  recent docs here:
  http://backreference.org/2014/03/20/some-notes-on-macvlanmacvtap/
  need to integrate in iproute and kernel docs.
  • receive side zero copy
 The ideal is a NIC with accelerated RFS support,
 So we can feed the virtio rx buffers into the correct NIC queue.
 Depends on non promisc NIC support in bridge.
 Search for "Xin Xiaohui: Provide a zero-copy method on KVM virtio-net"
 for a very old prototype
  • RDMA bridging
  • DMA emgine (IOAT) use in tun
 Old patch here: [PATCH RFC] tun: dma engine support
 It does not speed things up. Need to see why and
 what can be done.
  • virtio API extension: improve small packet/large buffer performance:
 support "reposting" buffers for mergeable buffers,
 support pool for indirect buffers
  • more GSO type support:
      Kernel not support more type of GSO: FCOE, GRE, UDP_TUNNEL
  • ring aliasing:
 using vhost-net as a networking backend with virtio-net in QEMU
 being what's guest facing.
 This gives you the best of both worlds: QEMU acts as a first
 line of defense against a malicious guest while still getting the
 performance advantages of vhost-net (zero-copy).
 In fact a bit of complexity in vhost was put there in the vague hope to
 support something like this: virtio rings are not translated through
 regular memory tables, instead, vhost gets a pointer to ring address.
 This allows qemu acting as a man in the middle,
 verifying the descriptors but not touching the packet data.
  • non-virtio device support with vhost
 Use vhost interface for guests that don't use virtio-net
  • Extend sndbuf scope to int64
 Current sndbuf limit is INT_MAX in tap_set_sndbuf(),
 large values (like 8388607T) can be converted rightly by qapi from qemu commandline,
 If we want to support the large values, we should extend sndbuf limit from 'int' to 'int64'
 Why is this useful?
 Upstream discussion: https://lists.gnu.org/archive/html/qemu-devel/2014-04/msg04192.html

vague ideas: path to implementation not clear

  • change tcp_tso_should_defer for kvm: batch more
 aggressively.
 in particular, see below
  • tcp: increase gso buffering for cubic,reno
   At the moment we push out an skb whenever the limit becomes
   large enough to send a full-sized TSO skb even if the skb,
   in fact, is not full-sized.
   The reason for this seems to be that some congestion avoidance
   protocols rely on the number of packets in flight to calculate
   CWND, so if we underuse the available CWND it shrinks
   which degrades performance:
   http://www.mail-archive.com/netdev@vger.kernel.org/msg08738.html
   However, there seems to be no reason to do this for
   protocols such as reno and cubic which don't rely on packets in flight,
   and so will simply increase CWND a bit more to compensate for the
   underuse.
  • ring redesign:
     find a way to test raw ring performance 
     fix cacheline bounces 
     reduce interrupts


  • irq/numa 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?
  • vlan filtering in bridge
       kernel part is done (Vlad Yasevich)
       teach qemu to notify libvirt to enable the filter (still to do) (existed NIC_RX_FILTER_CHANGED event contains vlan-tables)
  • tx coalescing
       Delay several packets before kick the device.
  • bridging on top of macvlan
 add code to forward LRO status from macvlan (not macvtap)
 back to the lowerdev, so that setting up forwarding
 from macvlan disables LRO on the lowerdev
  • virtio: preserve packets exactly with LRO
 LRO is not normally compatible with forwarding.
 virtio we are getting packets from a linux host,
 so we could thinkably preserve packets exactly
 even with LRO. I am guessing other hardware could be
 doing this as well.
  • vxlan
 What could we do here?
  • bridging without promisc mode with OVS

high level issues: not clear what the project is, yet

  • security: iptables

At the moment most people disables iptables to get good performance on 10G/s networking. Any way to improve experience?

  • performance

Going through scheduler and full networking stack twice (host+guest) adds a lot of overhead Any way to allow bypassing some layers?

  • manageability

Still hard to figure out VM networking, VM networking is through libvirt, host networking through NM Any way to integrate?

testing projects

Keeping networking stable is highest priority.

  • Write some unit tests for vhost-net/vhost-scsi
  • Run weekly test on upstream HEAD covering test matrix with autotest
  • Measure the effect of each of the above-mentioned optimizations
 - Use autotest network performance regression testing (that runs netperf)
 - Also test any wild idea that works. Some may be useful.
  • Migrate some of the performance regression autotest functionality into Netperf
 - Get the CPU-utilization of the Host and the other-party, and add them to the report. This is also true for other Host measures, such as vmexits, interrupts, ...
 - Run Netperf in demo-mode, and measure only the time when all the sessions are active (could be many seconds after the beginning of the tests)
 - Packaging of Netperf in Fedora / RHEL (exists in Fedora). Licensing could be an issue.
 - Make the scripts more visible

non-virtio-net devices

  • e1000: stabilize

test matrix

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