[PATCH net-next v2 0/3] Multiqueue support in virtio-net

[Jason Wang]

Hi all:

This series is an update version of multiqueue virtio-net driver based on
Krishna Kumar's work to let virtio-net use multiple rx/tx queues to do the
packets reception and transmission. Please review and comments.

A protype implementation of qemu-kvm support could by found in
git://github.com/jasowang/qemu-kvm-mq.git. To start a guest with two queues, you
could specify the queues parameters to both tap and virtio-net like:

./qemu-kvm -netdev tap,queues=2,... -device virtio-net-pci,queues=2,...

then enable the multiqueue through ethtool by:

ethtool -L eth0 combined 2

Changes from V1:
Addressing Michael's comments:
- fix typos in commit log
- don't move virtnet_open()
- don't set to NULL in virtnet_free_queues()
- style & comment fixes
- conditionally set the irq affinity hint based on online cpus and queue pairs
- move the virnet_del_vqs to patch 1
- change the meaningless kzalloc() to kmalloc()
- open code the err handling
- store the name of virtqueue in send/receive queue
- avoid type cast in virtnet_find_vqs()
- fix the mem leak and freeing issue of names in virtnet_find_vqs()
- check cvq during before setting the max_queue_pairs in virtnet_probe()
- check the cvq and VIRTIO_NET_F_RFS in virtnet_set_queues()
- set the curr_queue_pairs in virtnet_set_queue()
- use the err report by virtnet_set_queue() as the return value of
  ethtool_set_channels()

Changes from RFC v7:
Addressing Rusty's comments:
- align the implementation (location of cvq) to v5.
- fix the style issue.
- use a global refill instead of per-vq one.
- check the VIRTIO_NET_F_RFS before calling virtnet_set_queues()

Addresing Michael's comments
- rename the curr_queue_pairs in virtnet_probe() to max_queue_pairs
- validate the number of queue pairs supported by the device against
  VIRTIO_NET_CTRL_RFS_VQ_PAIRS_MIN and VIRTIO_NET_CTRL_RFS_VQ_PAIRS_MAX.
- don't crash when failing to change the number of virtqueues
- don't set the affinity hint when onle single queue is used or there's too much
  virtqueues
- add a TODO of handling cpu hotplug
- allow user to set the nubmer of queue pairs between 1 and max_queue_pairs

Changes from RFC v6:
- Align the implementation with the RFC spec update v5
- Addressing Rusty's comments:
  * split the patches
  * rename to max_queue_pairs and curr_queue_pairs
  * remove the useless status
  * fix the hibernation bug
- Addressing Ben's comments:
  * check other parameters in ethtool_set_queues

Changes from RFC v5:
- Align the implementation with the RFC spec update v4
- Switch the mode between single mode and multiqueue mode without reset
- Remove the 256 limitation of queues
- Use helpers to do the mapping between virtqueues and tx/rx queues
- Use commbined channels instead of separated rx/tx queus when do the queue
  number configuartion
- Other coding style comments from Michael

Changes from RFC v4:
- Add ability to negotiate the number of queues through control virtqueue
- Ethtool -{L|l} support and default the tx/rx queue number to 1
- Expose the API to set irq affinity instead of irq itself

Changes from RFC v3:
- Rebase to the net-next
- Let queue 2 to be the control virtqueue to obey the spec
- Prodives irq affinity
- Choose txq based on processor id

Reference:
- Virtio spec RFC: http://patchwork.ozlabs.org/patch/201303/
- V1: https://lkml.org/lkml/2012/11/27/177
- RFC V7: https://lkml.org/lkml/2012/11/27/177a
- RFC V6: https://lkml.org/lkml/2012/10/30/127
- RFC V5: http://lwn.net/Articles/505388/
- RFC V4: https://lkml.org/lkml/2012/6/25/120
- RFC V2: http://lwn.net/Articles/467283/

Perf Numbers:

Will do some basic test and post as a reply to this mail.

Jason Wang (3):
  virtio-net: separate fields of sending/receiving queue from
    virtnet_info
  virtio_net: multiqueue support
  virtio-net: support changing the number of queue pairs through
    ethtool

 drivers/net/virtio_net.c        |  726 +++++++++++++++++++++++++++++----------
 include/uapi/linux/virtio_net.h |   27 ++
 2 files changed, 567 insertions(+), 186 deletions(-)

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