The kernel column by Jon Masters #82

Character devices for network interfaces:
As anyone who has worked with a major Linux distribution vendor will tell you, one of the most annoying problems faced by many large-scale Linux deployments is that of inconsistent device naming. A corporation may purchase many thousands of identical systems, only to find that minor differences in system revision, PCI topology and even the hardware MAC addresses of network interfaces can result in device names being inconsistent between systems. One box sees a device as eth0, while the other sees it as eth1, eth2, or something else. It’s especially a problem for those using common system disk images, or moving disks between systems, so I was very pleased to see that the folks at Dell (who are typically excellent at working with the community on kernel issues) have proposed a new character device interface exposing the mapping between device names and devices. In the mid-term it should be possible to automatically handle any differences.

Fast symbol resolution:
Alan Jenkins has been doing some great work on the Linux Kernel Module (LKM) module loader and tools over the past few years. I have had the privilege to work with him a number of times in my capacity as maintainer of some of those tools, and am always impressed by his work. The latest patches add support for a binary searchable kernel symbol index, generated during the kernel compilation and used by the running kernel for more expediently resolving symbols needed by modules. With this work, the kernel takes even less time to boot on modern netbook systems like his.

KVM para-virtualisation improvements:
KVM (Kernel-based Virtual Machine) enables users to exploit modern hardware virtualisation features available on Intel-compatible systems. The (optional) para-virtualisation features go a stage further by allowing virtualisation-aware guests’ operating systems running under KVM to take advantage of improved performance optimisations. For example, a recent modification to KVM allows for para-virtualised guests experiencing a page fault (due to memory being temporarily in on disk swap space) to suspend only the faulting guest OS process and not the entire guest. The guest is then free to continue running other processes while the host machine running KVM completes the faulting in of the necessary data.