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Kernel trends: Outlook on 3.3

Directly after the release of Linux 3.2, the first, usually two-week long, merge window of the Linux kernel development cycle will start, during which the kernel developers incorporate the many changes for the next version of the kernel into the main development branch. Numerous changes have already been prepared for this first phase of the next development cycle.

Some Android-specific drivers that were thrown out of the staging area with Linux 2.6.33 in spring 2010 are likely to be reintroduced in Linux 3.3, as staging maintainer Greg Kroah-Hartman has incorporated them into the development branch that contains his planned changes for Linux 3.3 (1, 2); other components to be included in the staging area of Linux 3.3 include the pmem driver and a few other Android-specific changes. In a Google+ posting, Greg Kroah-Hartman explains that the kernel now contains almost all of the components required to boot an Android system's userspace. However, the developer points out that these are by no means all of the kernel extensions included in Android; among the components that are still missing is the wakelock code, which is not required to boot but prolongs the system's battery life.

Parts of the graphics driver for Intel's Poulsbo (US15W) are scheduled to leave the staging area. Originally, the developers had planned to introduce kernel-side LTTng (Linux Trace Toolkit) support to the staging area in Linux 3.3; however, they aborted their plan after it was criticised. A component with realistic chances of being included is the uprobesPDF userspace tracing solution; this approach can be used by tools such as SystemTap, it has the support of quite a few kernel developers and has been part of Linux-Next for several weeks. Background information can be found in an older article on LWN.net and in the most recent patch submission which includes a documentation file and perf support.

Linux 3.3 is scheduled to provide the patch that will allow the kernel to behave like modern Windows versions when deciding whether to disable or enable ASPM on a system level. A likely addition to the network subsystem will be Open vSwitch, a multilayer virtual switch that is used in, for example, XenServer 6.0. The developers also plan to integrate the code for implementing an ethernet teaming device into 3.3; it is intended as a fast, simple and userspace-driven alternative to the existing bonding driver and allows the bundling of multiple network adapters. In a Google+ posting, the network stack developers said that they plan to introduce byte queue limiting support, which is designed to reduce the latency that is caused by overly long queues in the hardware ("buffer bloat") without reducing data throughput.

As usual, the Kernel Log will summarise these and other developments in the Linux kernel field – including new point releases of the stable kernel series (3.2.y), which should, over the next few weeks, fix a few bugs that testers missed during development or which hackers could not fix in time for the release of Linux 3.2. The Kernel Log in The H Open will, as usual, be reporting on the major changes integrated into the next kernel version in a "Coming in 3.3" mini series. A release of 3.3 in early or mid March seems likely at this point in time. A detailed summary of the major changes in 3.3 will then be published on The H Open in a Kernel Log like this one.

Further background information about the developments in the Linux kernel area can be found using the search function at The H Open Source. Information about previous Linux kernel releases can be found in The H's Linux Kernel History. New editions of Kernel Logs are also mentioned on Identi.ca and Twitter by @kernellog2. The Kernel Log author also posts updates about various topics on Identi.ca and Twitter as @kernellogauthor.

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