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Linux 3.2 goes bigtime on file systems, improves thin provisioning

Jan 5, 2012 — by Eric Brown — from the LinuxDevices Archive — views

[Updated: Jan. 9] — Linus Torvalds announced the release of the Linux 3.2 kernel, featuring file-system enhancements such as support for larger block sizes in Ext4, and faster scrubbing with Btrfs. Other Linux 3.2 highlights are said to include process scheduler improvements, better thin provisioning support in the Device Mapper, improved desktop responsiveness for heavy write-backs, and new Wi-Fi and graphics drivers.

The Linux 3.2 kernel arrived a few days late, according to Linux creator and overseer Linus Torvalds in his Jan. 4 announcement. That's a vast improvement over Linux 3.1, however, which was released several weeks late in October due to an earlier outbreak of malware attacks against the kernel's home at

Linux 3.1 offered enhancements to performance, virtualization, and power management, as well as support for near field communication (NFC). Linux 3.2, meanwhile, refocuses on a central concern of kernel enhancements: the file-systems.

According to the official Linux 3.2 changelog on, one of the most prominent new features is the addition of large file support on the mainstream Ext4 file system. Ext4 now supports block sizes larger than 4KB and as big as 1MB.The still experimental Btrfs file system, meanwhile, has been updated with faster scrubbing, more detailed corruption messages, and manual inspection tools, says the changelog. Btrfs is also said to have been upgraded with automatic backup of critical filesystem metadata.

Process bandwidth control and "dirty throttling"

The kernel's process scheduler now offers a process bandwidth controller that provides support for setting upper limits of CPU time. In addition, desktop responsiveness has been improved for heavy data write-back applications, using a technique called "I/O-less dirty throttling," according to the changelog. In the area of memory handling, "cross memory attach" enhancements have been added to allow read/write to and from another process' address space.

In networking, the TCP stack now includes an algorithm that speeds the recovery of the connection after lost packets, says In addition, the "perf top" profiling tool has added support for live inspection of tasks and libraries, as well as the ability to view the annotated assembly code.

The Linux 3.2 kernel's Device Mapper has added support for thin provisioning of storage, providing for greater flexibility and efficiency in provisioning storage capacity to multiple users. The technology helps system administrators avoid over-provisioning storage for users who do not need it, explains the changelog.

Hexagon support leads driver changes

The kernel now supports Qualcomm's Hexagon digital signal processor (DSP), says the changelog. Other driver improvements include support for the DRM/KMS driver for Intel GPUs (graphics processing units). This will enable the more efficient and Intel-specific RC6 graphics power-saving feature by default, according to an analysis of the Linux 3.2 kernel in The H by Thorsten Leemhuis.

In addition, Leemhuis notes that the Nvidia Nouveau driver now uses the acceleration functions that are available with the auto-generated firmware on the Fermi graphic cores NVC1, NVC8, and NVCF.

Finally, Wi-Fi driver changes include the advancement of Broadcom's Brcmsmac and Brcmfmac Brcm80211 drivers from the staging area into the network subsystem. Also advancing to the subsystem is the Ath6kl Wi-Fi driver for the Atheros' AR6003 chip, writes Leemhuis.

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