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Linux kernel 2.6.23 brings new scheduler, more

Oct 18, 2007 — by LinuxDevices Staff — from the LinuxDevices Archive — views

Analysis — The newest Linux kernel, released earlier this month, adds a desktop-oriented scheduler, better memory management, more ALSA and other device drivers, and enough new virtualization features to make Linux the most virtualization-friendly of all the operating systems.

Linux is in a state of constant evolution. The latest step forward, Linux 2.6.23, arrived earlier this month. What's it all about?

In a note to the LKML (Linux kernel mailing list), Linux creator Linus Torvalds announced that while Linux 2.6.23 had been delayed, it wasn't “because of any huge issues, but because of various bug fixes trickling in and causing me to reset my 'release clock' all the time. But it's out there now, and hopefully better for the wait.”

Here's what's “better” in this release…

First, the kernel contains a new process scheduler: CFS (completely fair scheduler). CFS is designed to dynamically manage and track how much time a task is given and used for by the computer. The object is to make the most efficient possible use of the CPU for whatever programs are running at the time.

Believe it or not, an enormous argument sprang up about how “fair” the CFS was, and how fair the decision was to go with CFS over the alternative RSDL/SD scheduler. After several weeks of heated debate, which seemed to be half about which scheduler was better and half about software engineers' egos, the fuss cooled down.

This kernel version also features even more virtualization support. Linux is, without a doubt, quickly becoming the most virtualization-friendly of all the operating systems. In 2.6.23, the kernel changes added more support for Xen, KVM, and the new, Linux-on-Linux lguest virtualization hypervisor.

The new kernel also boasts improved memory management. As with all operating systems, Linux's memory management can sometimes be a problem. Now, with the oddly-named memory reclaiming algorithm, “lumpy,” Linux should be able to do a better job of freeing up memory. This, combined with a new way of flagging memory that can be moved, should result in more efficient memory utilization even after a computer has been in use for a long time, with multiple programs loading, running, and exiting.

Last, but never least, what would a new Linux kernel be without more device drivers? This time around there are dozens of new drivers for everything from SCSI drives to WiFi cards to graphic cards and back again. Perhaps the most important of these is the continued move of Linux from OSS (Open Sound System) to ALSA (Advanced Linux Sound Architecture) for audio support. While the transition still isn't complete, as more and more devices gain ALSA drivers, OSS will become a relic standard.

Steven J. Vaughan-Nichols

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