Linus Torvalds announced the release of a stable Linux 2.6.32
kernel. Major additions include kernel-based mode setting (KMS)
and 3D graphics support on select Radeon cards, plus new kernel
shared memory (KSM) technology for KVM virtualization,
power-saving and performance improvements, and a faster "Devtmpfs"
Many of the recent Linux kernel releases have focused on
filesystems, such as September's Linux 2.6.31, which was notable
primarily for adding USB 3.0 support, but also offered a much more
robust implementation of the Btrfs filesystem. Before that, Linux
2.6.30 added the NILFS2, EXOFS, and POHMELFS filesystems, and
Linux 2.6.29 debuted the embedded-oriented Squashfs filesystem, as
well as the first implementation of Btrfs.
With Linux 2.6.32, however, "I think we have a release without any
actual new filesystem for once," writes Torvalds (pictured at top)
in the announcement. "But there's been a fair amount of changes to
btrfs, and the block layer writeback itself has been through major
updates, and the whole per-bdi writeback thing is a pretty big
change. Other rather noticeable changes are in . . . drivers all
over the place."
Over at The H, Thorsten Leemhuis offers a thorough rundown on the
new kernel features, which are led by the support of KMS and 3D
graphics on AMD/ATI's series 2000, 3000 and 4000 Radeon graphics
cards. Improving 3D graphics support should help improve Linux'
standing as a gaming platform, among other benefits.
Meanwhile, performing mode-setting for graphics card resolution
and depth mode settings in kernel-space (KMS) offers advantages
over user-based mode-setting, such as increased flexibility and
security in case of a fatal error in the kernel. As welcome as
these developments are in bringing Linux up to snuff for graphics,
Leemhius notes that ATI just released Radeon series 5000 graphics
cards, which are supported only by generic VESA open source driver.
KSM improves virtualization performance
Not to be confused with KMS is the new kernel shared memory (KSM)
technology, which "merges identical memory pages from different
userland processes to reduce memory usage in virtualized
environments and make more efficient use of hardware," writes
Leemhuis. Also referred to as "Kernel SamePage Merging," KSM
derives from the KVM virtualization community. KSM is said to scan
the memory of multiple userland processes for identical areas, and
then combines any matches, improving performance by reducing the
memory load. This is particularly useful when "multiple similar
guest operating systems share the same software libraries and
programs run on a computer, causing large areas of the data stored
in the guests' memory to be identical," he adds.
With improvements such as KSM over recent kernel releases, KVM has
been improved to the point that it "has prompted Linux heavyweight
Red Hat to shift the focus away from Xen, which was all the rage
in the field of virtualization a few years ago," writes Leemhuis.
Devtmpfs promises faster kernel boots
The somewhat controversial "Devtmpfs" boot system, meanwhile, was
said to be favored by Torvalds. Devtmpfs "should mean that the
Linux kernel boots faster and no longer requires udev, while new
make targets will allow testers to easily generate kernel
configurations adapted to their systems," writes Leemhuis.
The "per-bdi writeback thing" mentioned by Torvalds is a "major
rewrite of the writeback infrastructure," according to Leemhuis,
resulting in each device now being linked to its own "per-BDI"
thread. Along with other improvements, the writeback overhaul
"should significantly increase data throughput for
writeback-intensive access scenarios and cause them to run more
evenly," he adds.
Other improvements include support for Intel's upcoming Moorestown
processor platform, which is aimed primarily at MIDs, and major
changes to the power management code. Meanwhile, performance has
been improved in a variety of ways, including enhancements to the
Cpuidle framework, the block layer, and Btrfs, according to Leemhuis.
"Linux 2.6.32 should not only allow PCs to push more data around,
it should also feel faster, with changes to the block layer and
the process scheduler promising better reactivity," he adds.
Linus Torvalds' announcement of Linux 2.6.32 stable may be found
here, and the kernel itself may be downloaded at kernel.org, here.