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Sitting at the heart of every Linux OS distribution is a Linux kernel. When it comes to the upcoming Red Hat Enterprise Linux (RHEL) 6 release, the issue of which kernel is being used is not a cut and dried answer, however.

The enterprise Linux OS vendor goes its own way when it comes to including a Linux kernel in its RHEL 6 release.

RHEL 6 is currently in its first beta release, with a feature freeze now in place. Currently, the mainline Linux kernel is nearing its 2.6.34 release, while the most recent stable release is the 2.6.33 release, which came out in February. But instead of either sticking with the 2.6.33 Linux kernel or holding out for 2.6.34, Red Hat is taking a different approach.

“We do have pieces of 2.6.34, as well as the preceding kernel versions in RHEL 6,” Tim Burke, vice president of platform engineering at Red Hat (NYSE: RHT), told “So there is no one [kernel version] number that accurately represents the RHEL 6 kernel. We take what is upstream; if there are pieces that are not mature, we disable them so they don’t disrupt things; and there are some technology pieces that are further ahead that we pull in.”

As a result of RHEL’s approach, its kernel is a hybrid of best-of-breed technologies. And it’s in keeping with earlier Red Hat releases. Back in 2004, Red Hat was backporting features from the Linux 2.6 kernel into its own 2.4 Linux kernel. The Red Hat approach to backporting features was praised at the time by Linux creator Linus Torvalds.

According to Burke, “When we ship a kernel in any RHEL product, we don’t just take the upstream kernel, drop it in and ship it.”

“We are the No. 1 contributor to Linux and that’s borne out by stats,” he added. “Because we’re the leading contributor to Linux, we always have lots of initiatives and projects underway. Some of these initiatives are short-term while others are longer-term.”

According to the latest “Who Writes Linux” report from the Linux Foundation, Red Hat contributed 12 percent of all change contributions to the Linux 2.6.30 kernel. IBM (NYSE: IBM) came in at second place with 6.3 percent, Novell (NASDAQ: NOVL) third at 6.1 percent and Intel (NASDAQ: INTC) fourth at 6.0 percent.

Real-Time Linux Features in RHEL 6

Among the longer-term Linux kernel efforts that Red Hat is pursuing is real-time capabilities, which enables the OS to deliver deterministic performance. That ensures actions are executed within the same amount of time, every time, which is a critical feature for industries like the military and financial services.

Some of Red Hat’s real-time Linux kernel efforts are being included in RHEL 6, though the company has a separate real-time kernel that is part of its MRG release, which tracks the latest in real-time innovations.

“RHEL 6 has benefited from a fairly sizable subset of the work we’ve done in real time for MRG, which has since been incorporated upstream,” Burke said.

There is still working ongoing with the MRG real-time kernel, which Burke described as a continuum of enhancements. To date, he noted that MRG has been focused on the core subsystems of CPU scheduling and timers. As a result, he added that there is still ground to cover with improvements in the I/O and networking stacks.

“There will continue to be separate MRG real-time kernel offering targeted at customers that need the absolute finest grain of determinism in their applications,” Burke said.

Sean Michael Kerner is a senior editor at, the news service of, the network for technology professionals.

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