Features/VHostNet

Enable kernel acceleration for kvm networking

Summary

Enable kernel acceleration for kvm networking

Owner

• Name: Michael S. Tsirkin

Current status

• Targeted release: Fedora 12
• Last updated: 2009-06-06
• Percentage of completion: 20%

Detailed Description

vhost net moves the task of converting virtio descriptors to skbs and back from qemu userspace to the kernel driver.

Benefit to Fedora

Using a kernel module reduces latency and improves packets per second for small packets.

Scope

The work is all upstream in the kernel and qemu. Guest code is already upstream. Host/qemu work is in progress. For Fedora 12 will likely have to backport some of it.

Milestones:

- Guest Kernel:

 MSI-X support in virtio net

- Host Kernel:

 iosignalfd, irqfd, eventfd polling
 finalize kernel/user interface    
 socket polling                    
 virtio transport with copy from/to user

 <- at this point can be used in production the rest are optimizations
    we will most likely need                                          

 mergeable buffers
 TX credits using destructor (or: poll device status)
 TSO/GSO                                             
 pin memory with get user pages                      
 profile and tune                                    

- qemu:

 MSI-X support in virtio net
 raw sockets support in qemu, promisc mode
 connect to kernel backend with MSI-X     
 migration                                
 PCI interrupts emulation                 

 <- at this point can be used in production
    the rest are optimizations we will most likely need

 programming MAC
 TSO/GSO        
 profile and tune

Test Plan

Guest:

• WHQL networking tests

Networking:

• Various MTU sizes
• Broadcasts, multicasts,
• Ethtool
• Latency tests
• Bandwidth tests
• UDP testing
• Guest to guest communication
• More types of protocol testing
• Guest vlans
• Tests combination of multiple vnics on the guests
• With/without {IP|TCP|UDP} offload

Virtualization:

• Live migration

Kernel side:

• Load/unload driver

User Experience

Users should see faster networking at least in cases of SRIOV or a dedicated per-guest network device.

Dependencies

• kernel acceleration is implemented in the kernel rpm and depends on changes in qemu-kvm to work correctly.

Contingency Plan

• We don't turn it on by default if it turns out to be unstable.

Comments and Discussion

• See Talk:Features/VHostNet