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Linux 2.6.37 boosts SMP, loads up on drivers

Jan 7, 2011 — by Eric Brown — from the LinuxDevices Archive — views

The Linux 2.6.37 kernel was released this week with improved symmetric multiprocessing (SMP) scalability and the addition of many new hardware drivers. Other 2.6.37 highlights include security, power management and memory management enhancements, plus an I/O throttling speed boost and an option to disable the Big Kernel Lock.

While the tech world's attention has been drawn to the Consumer Electronics Show in Las Vegas, the kernel behind many of the hottest new tablets, smartphones, media servers, and other devices at the show received an upgrade.

The Linux kernel, which underlies Android, MeeGo, WebOS, Chrome OS, and numerous no-name embedded OS implementations — not to mention Ubuntu and other desktop Linux distros, plus a good share of the world's servers — has now emerged in its 2.6.37 incarnation. 

Announced by Linux creator Linus Torvalds (pictured) on Jan. 4, Linux 2.6.37 follows up on an October release of Linux 2.6.36, which featured the integration of the AppArmor security framework. That release also introduced support for the Tilera multicore architecture, a redesign of workqueues, an Out-of-Memory (OOM) killer, debugging and latency enhancements, and a partial implementation of VFS virtualization scalability patches.

SMP speed-ups and the end of BKL

IDG News reports that a key enhancement to the new kernel relates to symmetric multiprocessing (SMP) scalability. In particular, the ext4 and XFS file-systems have been enhanced to better handle SMP, which is used in multicore and multiprocessor systems.

Ext4, for example, no longer uses a buffer layer to communicate. As a result, SMP-focused benchmarks (using a 48-core system connected to a 24-unit SAS storage array) showed ext4 accelerating 192 simultaneous FFSB (Flexible File System Benchmark) threads by 300 percent. They also showed it reducing the load on the CPUs by a factor of three or four, says the story.

XFS has also been improved to offer markedly faster SMP handling, writes Jackson.

Related to SMP, the outdated Big Kernel Lock (BKL) technology, which has gradually been extricated from the kernel, has now been essentially neutered, as developers now have an option to avoid it entirely. Although originally implemented to enhance SMP scalability, BKL became a hindrance on larger-scale SMP deployments, significantly slowing operations.

As Jackson writes, "Developers have subsequently pioneered more fine-grained locking techniques that eliminate the need to run BKL."

Drivers, drivers everywhere

Another big story, on a cumulative level, is the unusually large number of new hardware drivers in the new kernel. "Linux 2.6.37 promises to take hardware compatibility to new levels," writes Katherine Noyes at PC World.

New video drivers, for example, include improved i915, Nouveau and Radeon drivers, and new networking drivers include "carl9170" for AR9170 802.11n devices from Atheros, which will soon be acquired by Qualcomm. In addition, there's a new gigabit Ethernet driver for the Topcliff PCH and a driver for the Brocade BNA 10GB Ethernet, among many others, writes Noyes.

Linux 2.6.37 also adds support for I/O throttling, enabling developers to set upper read/write limits on a group of processes in order to boost performance, says the story. New power management features, meanwhile, are said to include a delayed device autosuspend feature that improves runtime power management, as well as the addition of LZO hibernation compression.

SELinux and memory management enhancements

At's LinuxPlanet, meanwhile, Sean Michael Kerner takes a closer look at the new kernel's security and memory management improvements. SELinux (Security Enhanced Linux) has been upgraded with a fast status update interface from NEC, as well as with a patch from Red Hat developer Eric Paris that enables userspace to read policy back out of the Linux kernel, says the story.

In addition, the kernel now supports the IPv tunnel mode and 'Any-IP' support for IPv6. The Any-IP patch receives packets and establishes incoming connections on IPs that have not been explicitly configured, writes Kerner.

Finally, memory management has been enhanced with a Google-authored patch that provides new retry page fault when blocking on disk transfer patch, says the story. As a result, read access will jump from 55 iterations per second to 15,000 iterations per second, claims the patch developer.

Kerner quotes Novell Linux kernel developer Michal Hocko as saying about the patch, "This looks like a nice improvement for some multithreaded programs, specifically those where many threads perform mmap or other operations related to memory layout and heavy concurrent I/O takes place through such memory areas."

Linux trends for 2011

In other Linux coverage, our sister publication eWEEK published a wide-ranging overview of recent Linux trends earlier this week. The Fahmida Rashid piece starts by looking at Linux's role in Android and MeeGo, and discusses Canonical's push to move Ubuntu to tablets, starting with a Tenq P07 tablet in China.

Rashid also examines Canonical's decision to abandon the X Window interface in favor of Wayland for Ubuntu's graphical stack. Finally, she reports on the fork of the LibreOffice application suite from Oracle's OpenOffice, and looks at new open source drivers from Broadcom and AMD.


Linus Torvalds' Linux 2.6.37 announcement may be found here.

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