Kernel Log: First release candidate for Linux 3.1

by Thorsten Leemhuis

Expected to be released in about two months, the next kernel version will offer optimised virtualisation, add bad block management components to the software RAID code and include an extended Nouveau driver for NVIDIA's Fermi graphics chips. Several developers have been criticised for their clumsy use of Git in this development cycle.

Linus Torvalds has issued the first release candidate of Linux 3.1, closing the merge window of this version, whose final release is expected in late September or early October, 17 days after the release of Linux 3.0. Therefore, the first phase in the Linux development cycle was three days longer than usual. This was caused by the diving holiday Torvalds is currently taking in Hawaii; he is providing an impression of his trip on Google Plus.

Kernel development has now entered the stabilising phase, which Torvalds and his co-developers mainly use to fix bugs; no further major changes are usually integrated in this phase, and the most important advancements of Linux 3.1 can therefore already be outlined. For instance, the code for software RAIDs will, on some RAID levels, be able to handle media that contain defective blocks.

A large number of improvements have been made in the area of virtualisation. For example, KVM now offers the basic functionality that allows guest systems to be started from another guest system (nested virtualisation) on Intel processors. The XEN Dom0 code now supports text output via the VGA console and can pass through PCI devices to guests. Zero-copy support for macvtap and vhost-net is designed to improve network performance in virtualised environments.

As usual, the developers have integrated hundreds of changes to improve the kernel's hardware support; among the new additions is the rtl8192de Wi-Fi driver for Realtek's RTL8192DE and RTL8188DE PCIe Wi-Fi chips. The Nouveau driver now auto-generates firmware for the Fermi graphics chips that are used in GeForce series 400 and 500 hardware; when combined with current Mesa 3D and X.org drivers, this capability gives access to some of these graphics chips' 3D functions.

The "Native KVM tool" the developers introduced last spring was left out, but may yet follow in Linux 3.2; the cpupower diagnostic tool, on the other hand, did get integrated. Over the coming weeks, the Kernel Log will discuss these and other changes in a "Coming in 3.1" mini-series of articles.

Latest kernel version status

A few days ago, Andi Kleen released Long-term kernel version 2.6.35.14. Greg Kroah-Hartman followed soon afterwards with Stable kernel 2.6.39.4 and said in his release email that this will be the last Linux 2.6.39-based version; he advised all users to switch to Linux 3.0. When asked whether 2.6.39 will become a Long-term kernel, Kroah-Hartman replied that there are no plans to this effect. The developer said that he sees no reason why 2.6.39 should become a Long-term kernel, adding that the version jump to 3.0 didn't introduce any conceptual changes that didn't already exist in 2.6.39.

At the end of the first week of August, the developers released the first Linux 3.0-based Stable kernel, Linux 3.0.1. It offers about one hundred changes; the release email contains the usual recommendation to change to the new version without specifying any particular reasons why.

In brief

Kernel

The developers of the Linux real-time extensions have continued their work on the Realtime/RT patches for Linux 3.0; the recently introduced version 7 reintroduced highmem support for i386/x86-32 processors, while version 8 offers various corrections.

On his blog, GlusterFS developer Jeff Darcy lists various Posix functions that are not supported by FUSE (File System in Userspace).

Stephen Rothwell has reorganised the Git branch of Linux-Next so that this branch only contains versions from the past three months; older versions are now located in "linux-next-history".

With the version jump to Linux 3.0, it seemed that there would be no kernel version 2.6.40; however, Fedora 15 users have received such a version as part of their regular updates in the past few days. This is a Linux 3.0 kernel which the Fedora developers have given version number 2.6.40 – a measure designed to avoid problems with programs that could become confused by a leading "3" in the version number.