Linux 3.6 Delivers Solid Progress
Linux creator Linus Torvalds released the fifth new major Linux kernel release of 2012 late Sunday. The new kernel provides incremental improvements to multiple aspects of the open source operating system.
The Linux 3.6 release follows the Linux 3.5 release that debuted at the end of July and provided new stability improvement to Linux.
"There haven't been any huge new architectures or filesystems — it's all 'solid progress,'" Torvalds wrote in his release announcement. "That may not sound all that exciting, but the devil is in the details, and there's a lot of small fixes all over."
On the filesystem side, Linux 3.6 delivers a set of enhancements to the Btrfs filesysem. Btrfs is an open source filesystem originally started by Oracle developer Chris Mason that provides advanced snapshotting and other next generation features. For Linux 3.6, Btrfs gains new quota controls with quota groups and subvolume quotas.
Linux now also gains the ability to suspend to both memory and disk simultaneously.
"It is often useful to suspend to memory after hibernation image has been written to disk," Linux developer Borjan Smojver wrote in his kernel commit message. "If the battery runs out or power is otherwise lost, the computer will resume from the hibernated image. If not, it will resume from memory and hibernation image will be discarded."
From a networking perspective, Linux 3.6 now includes support for TCP Fast Open (TFO). TFO provides a new optimized method for performing the initial TCP handshake in a data connection. TFO started off as a research effort led by Google, and the Linux 3.6 kernel code was authored by Google developer Yuchung Cheng.
"Based on traffic analysis and network emulation, we show that TCP Fast Open would decrease HTTP transaction network latency by 15 percent and whole-page load time over 10 percent on average, and in some cases up to 40 percent," Cheng and his co-authors wrote in a 2011 research paper introducing TFO.
Thanks to Red Hat, Linux 3.6 also benefits from a new VFIO (Virtual Function I/O) driver.
Red Hat developer Alex Williamson explained in his documentation for VFIO that modern systems now provide DMA and interrupt remapping facilities to help ensure I/O devices behave within the boundaries they've been allotted. Those systems include both AMD-Vi and Intel VT-d on x86.
"The VFIO driver is an IOMMU/device-agnostic framework for exposing direct device access to userspace, in a secure, IOMMU-protected environment," Williamson said. "In other words, this allows safe, non-privileged, userspace drivers."
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