As multi-queue nics were commonly used for high-end servers, current single queue based tap can not satisfy the requirement of scaling guest network performance as the numbers of vcpus increase. So the following series implements multiple queue support in tun/tap.
In order to take advantages of this, a multi-queue capable driver and qemu were also needed. I just rebase the latest version of Krishna's multi-queue virtio-net driver into this series to simplify the test. And for multiqueue supported qemu, you can refer the patches I post in http://www.spinics.net/lists/kvm/msg52808.html. Vhost is also a must to achieve high performance and its code could be used for multi-queue without modification. Alternatively, this series can be also used for Krishna's M:N implementation of multiqueue but I didn't test it. The idea is simple: each socket were abstracted as a queue for tun/tap, and userspace may open as many files as required and then attach them to the devices. In order to keep the ABI compatibility, device creation were still finished in TUNSETIFF, and two new ioctls TUNATTACHQUEUE and TUNDETACHQUEUE were added for user to manipulate the numbers of queues for the tun/tap. I've done some basic performance testing of multi queue tap. For tun, I just test it through vpnc. Notes: - Test shows improvement when receving packets from local/external host to guest, and send big packet from guest to local/external host. - Current multiqueue based virtio-net/tap introduce a regression of send small packet (512 byte) from guest to local/external host. I suspect it's the issue of queue selection in both guest driver and tap. Would continue to investigate. - I would post the perforamnce numbers as a reply of this mail. TODO: - solve the issue of packet transmission of small packets. - addressing the comments of virtio-net driver - performance tunning Please review and comment it, Thanks. --- Jason Wang (5): tuntap: move socket/sock related structures to tun_file tuntap: categorize ioctl tuntap: introduce multiqueue related flags tuntap: multiqueue support tuntap: add ioctls to attach or detach a file form tap device Krishna Kumar (2): Change virtqueue structure virtio-net changes drivers/net/tun.c | 738 ++++++++++++++++++++++++++----------------- drivers/net/virtio_net.c | 578 ++++++++++++++++++++++++---------- drivers/virtio/virtio_pci.c | 10 - include/linux/if_tun.h | 5 include/linux/virtio.h | 1 include/linux/virtio_net.h | 3 6 files changed, 867 insertions(+), 468 deletions(-) -- Jason Wang -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html