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Networking

The Berkeley packet filter (BPF), used by sniffer tools such as tcpdump, can now be used to filter VLAN tags. The rtl8723ae driver for the Realtek RTL8723AE PCIe WLAN chip is new (1, 2 and others). The brcmsmac WLAN driver now supports the BCM43224 Broadcom chip, while the rt2800usb RaLink driver supports the Sweex LW323 USB WLAN adapter. The cdc-mbim driver, which supports broadband modems that implement Mobile Broadband Interface Model (MBIM Direct download ) 1.0, specified PDF by the USB Implementers Forum, is also new (1, 2). MBIM is a USB protocol for connecting modems for laptops, tablets and desktop computers that provide an internet connection using GSM and CDMA-based 3G and 4G (including LTE).

Drivers

The kernel's audio drivers now support the Philips PSC724 Ultimate Edge sound card. The kernel can also handle VIA's VT1705CF HD audio codec now. Another addition is the mpt3sas "LSI MPT Fusion SAS 3.0 Device Driver" that supports 12GB SAS chips by LSI; it shares some features with the mpt2sas driver that has been put into maintenance mode. The hptiop driver can now address HighPoint RR4520 and RR4522 controllers. The kernel developers have marked the uas driver, which handles the USB Attached SCSI protocol, as broken because it causes problems and is not yet ready for the major distributions.

Infrastructure

Following a lengthy, sometimes heated dispute between various kernel developers, a number of enhancements developed under the "balancenuma" umbrella have been merged into Linux 3.8 (1, 2, 3, 4, 5 and others). In the ideal case, these improvements will enable the kernel to automatically maintain coherence between the processor and memory for a single process. This kind of setup is important for optimising performance on multiprocessor systems which utilise the now widely used NUMA (non-uniform memory access), as processes on NUMA systems can access memory allocated to the processor on which they are running faster than they can access memory allocated to other processors.

Architecture

Kernel Log penguin To simplify maintenance and ongoing development, the kernel developers have removed support for Intel 386 CPUs and other CPUs that make use of the architecture which was extremely widespread more than 20 years ago. 486 and newer x86-32 processors will continue to be supported. It was on a 386 that Torvalds first started developing Linux, but he will not be shedding any tears for the code, commenting: "I'm not sentimental. Good riddance."

Virtualisation

A balloon driver for Hyper-V has been merged into the kernel. The Microsoft hypervisor can, at runtime, temporarily transfer memory from Linux guests running this driver to the host and subsequently return it.

Linux 3.8 more or less completes the major restructuring around user namespaces, driven forward over the last few months by Eric W. Biederman. These changes will enable non-privileged users to create an isolated space within which they will have root privileges. Within this space, however users will not be able to do anything which would require privileged actions to be taken outside of the namespace.

Resource controls

The kmem extension has been added to the memory cgroup controller (1, 2 and others, documentation). It can be used to limit the amount of memory required by the kernel for managing processes. Using appropriately configured limits, this should enable the kernel to keep the lid on fork bombs even within containers.

Next: Summary, Outlook, Statistics

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