> RFC: Virtual-Bus (applies to v2.6.30-rc2)
> ----------------------
>
> Virtual-Bus is a Linux-kernel based virtual IO resource container technology.
> It allows you to declare virtualized device models directly within a host
> kernel that can be uniformly accessed from a variety of environments, such
> as KVM, userspace, lguest, Xen, etc. The goal is to reduce overhead while
> still preserving proper isolation to achieve maximum throughput and latency
> from your IO subsystem. It is installed on the host and configured using
> simple filesystem operations like "mkdir" to create a new container, "ln -s"
> to associate a device with a container, and "echo" to configure the device
> thanks to integration with configfs/sysfs. Therefore, managing a virtual-bus
> does not require special userspace tools.
>
> Why would we want this?
> ----------------------
>
> We believe that a combination of in-kernel models, coupled with optimizations
> in various areas such as reducing the number of context switches and executing
> the algorithms in parallel on modern multicore CPUs will result in the best
> possible IO performance for technologies such as virtualization. This
> facility aims to provide the framework for building such constructs in
> in software in the most efficient way we believe is possible.
>
> Preliminary Results:
> -----------------------
>
> As a test, we wrote a virtual-ethernet backend and a Linux driver
> (called venet) and tested the setup with v2.6.29 on two 8-core x86_64
> boxes with Chelsio T3 10GE connected back to back via cross over.
> We measured bare-metal performance, as well as a kvm guest (running the
> same kernel) connected to the T3 via a linux-bridge+tap configuration with
> a 1500 MTU. The results are as follows:
>
> Bare metal : tput = 4078Mb/s, round-trip = 25593pps (39us rtt)
> Virtio-net (PCI) : tput = 4003Mb/s, round-trip = 320pps (3125us rtt)
> Venet (VBUS): tput = 4050Mb/s, round-trip = 15255 (65us rtt)
>
> When we jump to 9000 byte MTU, the situation looks similar
>
> Bare metal : tput = 9717Mb/s, round-trip = 30396pps (33us rtt)
> Virtio-net (PCI) : tput = 4578Mb/s, round-trip = 249pps (4016us rtt)
> Venet (VBUS): tput = 5802Mb/s, round-trip = 15127 (66us rtt)
>
> Note that to be fair, part of the latency response from virtio-pci is due to
> the way that the driver/backend coalesces packets, and not a true limitation
> of the userspace path as the results may imply. Anthony Liguori is already
> looking into improving this based on the results we presented here, and is
> making good headway.
>
> Also note that as of v2, we support a virtio-vbus transport, and therefore
> will soon be able to compare "Virtio-net (VBUS)" as an additional target in
> the near future once we have developed a virtio-net backend for the host.
> This virtio-net(pci) to virtio-net(vbus) comparison is probably more
> interesting than comparing to Venet as it would be more apples to apples.
> Also it would be nice to only need one PV driver per IO subsystem in the
> long term.
>
> Changes v2->v3:
> ------------------
>
> *) VBUS now renders as a PCI/MSI device instead of via cpuid/dynirq
> *) Dropped dynirq (replaced with MSI facility)
> *) Dropped "reset" patch in favor of more reliably detecting reset via BUSOPEN
> *) Incorporated more review feedback from Stephen Hemminger on vbus-enet
> driver
> *) Added support for setting the guests MAC during host config (Pat Mullaney)
> *) Cleaned up documentation per feedback from Ben Hutchings
> *) Numerous small tweaks to clean up things like warnings, comments, etc.
> (Alex Tsariounov, Greg Haskins)
> *) Fixed Kconfig dependency problem with virtio-vbus with feedback from
> Peter Morreale.
>
> Changes v1->v2:
>
> *) Incorporated review feedback from Stephen Hemminger on vbus-enet driver
> *) Added support for connecting to vbus devices from userspace
> *) Added support for a virtio-vbus transport to allow virtio drivers to
> work with vbus (needs testing and backend models).
>
> Todo:
> *) Beef up the userspace event channel ABI to support different event types
> *) Add memory-registration support
> *) Develop some virtio backend devices.
> *) Support ethtool_ops for venet.
> *) Convert from MSI to MSIX to truely support multiple vectors
>
> ---------------------------------------
>
> For more details, please see our Wiki at
>
>
http://developer.novell.com/wiki/index.php/Virtual-bus
>
>
>
>
>
> ---
>
> Gregory Haskins (16):
> virtio: add a vbus transport
> vbus: add a userspace connector
> kvm: Add guest-side support for VBUS
> kvm: Add VBUS support to the host
> venettap: add scatter-gather support
> venet: add scatter-gather support
> venet-tap: Adds a "venet" compatible "tap" device to VBUS
> net: Add vbus_enet driver
> venet: add the ABI definitions for an 802.x packet interface
> ioq: add vbus helpers
> ioq: Add basic definitions for a shared-memory, lockless queue
> vbus: add a "vbus-proxy" bus model for vbus_driver objects
> vbus: add bus-registration notifiers
> vbus: add connection-client helper infrastructure
> vbus: add virtual-bus definitions
> shm-signal: shared-memory signals
>
> Patrick Mullaney (1):
> venet-tap: add the ability to set the client's mac address via sysfs
>
>
> Documentation/vbus.txt | 385 +++++++++
> arch/x86/Kconfig | 11
> arch/x86/include/asm/kvm_para.h | 1
> arch/x86/kvm/Kconfig | 9
> arch/x86/kvm/Makefile | 3
> arch/x86/kvm/x86.c | 6
> arch/x86/kvm/x86.h | 12
> drivers/Makefile | 2
> drivers/net/Kconfig | 13
> drivers/net/Makefile | 1
> drivers/net/vbus-enet.c | 898 +++++++++++++++++++++
> drivers/vbus/devices/Kconfig | 17
> drivers/vbus/devices/Makefile | 1
> drivers/vbus/devices/venet-tap.c | 1641 ++++++++++++++++++++++++++++++++++++++
> drivers/vbus/proxy/Makefile | 2
> drivers/vbus/proxy/kvm.c | 751 +++++++++++++++++
> drivers/virtio/Kconfig | 15
> drivers/virtio/Makefile | 1
> drivers/virtio/virtio_vbus.c | 496 +++++++++++
> fs/proc/base.c | 96 ++
> include/linux/ioq.h | 410 +++++++++
> include/linux/kvm.h | 7
> include/linux/kvm_host.h | 26 +
> include/linux/kvm_para.h | 58 +
> include/linux/sched.h | 4
> include/linux/shm_signal.h | 188 ++++
> include/linux/vbus.h | 166 ++++
> include/linux/vbus_client.h | 115 +++
> include/linux/vbus_device.h | 424 ++++++++++
> include/linux/vbus_driver.h | 80 ++
> include/linux/vbus_userspace.h | 48 +
> include/linux/venet.h | 82 ++
> include/linux/virtio_vbus.h | 163 ++++
> kernel/Makefile | 1
> kernel/exit.c | 2
> kernel/fork.c | 2
> kernel/vbus/Kconfig | 56 +
> kernel/vbus/Makefile | 11
> kernel/vbus/attribute.c | 52 +
> kernel/vbus/client.c | 543 +++++++++++++
> kernel/vbus/config.c | 275 ++++++
> kernel/vbus/core.c | 626 ++++++++++++++
> kernel/vbus/devclass.c | 124 +++
> kernel/vbus/map.c | 72 ++
> kernel/vbus/map.h | 41 +
> kernel/vbus/proxy.c | 216 +++++
> kernel/vbus/shm-ioq.c | 89 ++
> kernel/vbus/userspace-client.c | 485 +++++++++++
> kernel/vbus/vbus.h | 117 +++
> kernel/vbus/virtio.c | 627 +++++++++++++++
> lib/Kconfig | 21
> lib/Makefile | 2
> lib/ioq.c | 298 +++++++
> lib/shm_signal.c | 186 ++++
> virt/kvm/kvm_main.c | 10
> virt/kvm/vbus.c | 1392 ++++++++++++++++++++++++++++++++
> 56 files changed, 11380 insertions(+), 0 deletions(-)
> create mode 100644 Documentation/vbus.txt
> create mode 100644 drivers/net/vbus-enet.c
> create mode 100644 drivers/vbus/devices/Kconfig
> create mode 100644 drivers/vbus/devices/Makefile
> create mode 100644 drivers/vbus/devices/venet-tap.c
> create mode 100644 drivers/vbus/proxy/Makefile
> create mode 100644 drivers/vbus/proxy/kvm.c
> create mode 100644 drivers/virtio/virtio_vbus.c
> create mode 100644 include/linux/ioq.h
> create mode 100644 include/linux/shm_signal.h
> create mode 100644 include/linux/vbus.h
> create mode 100644 include/linux/vbus_client.h
> create mode 100644 include/linux/vbus_device.h
> create mode 100644 include/linux/vbus_driver.h
> create mode 100644 include/linux/vbus_userspace.h
> create mode 100644 include/linux/venet.h
> create mode 100644 include/linux/virtio_vbus.h
> create mode 100644 kernel/vbus/Kconfig
> create mode 100644 kernel/vbus/Makefile
> create mode 100644 kernel/vbus/attribute.c
> create mode 100644 kernel/vbus/client.c
> create mode 100644 kernel/vbus/config.c
> create mode 100644 kernel/vbus/core.c
> create mode 100644 kernel/vbus/devclass.c
> create mode 100644 kernel/vbus/map.c
> create mode 100644 kernel/vbus/map.h
> create mode 100644 kernel/vbus/proxy.c
> create mode 100644 kernel/vbus/shm-ioq.c
> create mode 100644 kernel/vbus/userspace-client.c
> create mode 100644 kernel/vbus/vbus.h
> create mode 100644 kernel/vbus/virtio.c
> create mode 100644 lib/ioq.c
> create mode 100644 lib/shm_signal.c
> create mode 100644 virt/kvm/vbus.c
>
> --
>
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