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02 April 2012, 12:01

Linux 3.4 goes into testing

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Linux Penguin Two weeks after Linux 3.3 was released, Linus Torvalds has announced the availability of the first release candidate for Linux 3.4. As usual, this step signals the end of the merge window at the beginning of the development cycle; during the merge window, Torvalds integrates the major changes for a new Linux version and about seven-eighths of all changes. Apart from a few stragglers, mainly minor and low-risk changes will be made in the stabilising phase that has now begun.

Among the new features that will be integrated into the new Linux version – expected to be released in late May – is kernel-side support for the x32 ABI. Programs that are compiled for this ABI can use the 64-bit registers and data paths of x86-64/x64 processors but only work with 32-bit pointers, which are more than sufficient for many typical tasks and use less memory than 64-bit pointers; roughly speaking, programs that are compiled for the x32 ABI therefore avoid the overhead that comes with full 64-bit operation while being able to use some of the main advantages of 64-bit processors.

The Hyper-V storage driver has moved from the staging branch to the SCSI subsystem. With this move, the last of the drivers for Microsoft's virtualisation interface has left the area for drivers that don't yet meet the kernel developers' quality requirements. Microsoft had released the drivers in July 2009, but initially did little to improve the code – the company did get its act together eventually. Background information on this learning and tuning process, and on the improvements that have been made over the years, can be found in the "Linux on Hyper-V – Our Journey Through The Linux Staging TreePDF" slides, a presentation the maintainers of these drivers at Microsoft plan to give at the Linux Foundation Collaboration Summit this week.

As previously mentioned, the kernel hackers have integrated drivers for new graphics cores by AMD and NVIDIA into the Linux main development branch. Only a few days later, one of the Nouveau developers released changes to the Nouveau drivers in Mesa 3D and that, together with the aforementioned kernel-side improvements, enable 2D and Xv acceleration on the latest GeForce graphics card; the developer also mentions that 3D support will hopefully follow soon.

Another patch integrated into version 3.4 of the Linux kernel is designed to fix a problem that causes the Intel driver to corrupt some memory areas after waking up from Hibernate (Software Suspend/ACPI S4). This modification has also been integrated into long-term and stable kernel versions 3.0.27, 3.2.14 and 3.3.1 that will each offer more than a hundred minor corrections and improvements; the review phase for these kernel versions closed on Sunday night, so the kernels should be released shortly.

So far, the developers have not integrated modifications into Linux 3.4 that allow Intel graphics drivers to use the RC6 power management technology by default in Sandy Bridge processors with graphics core. RC6 generally causes the power consumption of such CPUs to be reduced by 3 to 5 Watts when they are idle; according to a blog post by an Intel developer, the patches will probably be integrated into Linux 3.5.

The newly incorporated Yama security module can prevent processes from using the Ptrace (Process Trace) function call to examine other processes' memory; SELinux has recently acquired similar functionality. Over the coming weeks, the Kernel Log series at The H Open will discuss in detail these and various other new features that have been incorporated into Linux 3.4.

However, several changes that were presented on the LKML yesterday (1 April) are unlikely to make it into this, or any future, kernel version (1, 2, 3).

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