January 29, 2003 2:00 PM PST

Linux gets high-end server boost

Linux took a step forward in high-end servers with the recent adoption of software that should help IBM, NEC, SGI and others use the open-source operating system better in multiprocessor servers.

The improvement adds some support in Linux for nonuniform memory access, or NUMA, a design for higher-end servers with many processors. Linus Torvalds, the original creator of the operating system and still its top authority, accepted the update this month into version 2.5, the current test version of the software.

The change should help to keep Linux competitive with Unix--many versions of which already include the feature--and with Microsoft's Windows, which is due to receive it in April.

Many companies are settling on NUMA as the foundation for high-end, multiprocessor servers. Smaller servers have a single bank of memory, but larger multiprocessor servers often split memory into several areas. A processor trying to retrieve information will experience different--hence "nonuniform"--delays depending on how close the memory is to the processor using it.

Operating systems can be adjusted to compensate for this memory-response difference by making sure that data is stored in the nearest memory. Support for NUMA is a feature of Windows Server 2003, Microsoft announced last year. That operating system is due for release in April.

Standard support for NUMA in Linux won't arrive until later this year, in version 2.6 of the software. The NUMA software is being worked on and refined in version 2.5, the testing ground for 2.6.

NUMA servers designed to run Linux include IBM's 16-processor x440 and its upcoming x450; NEC's Express 5800/1000; and SGI's 64-processor Altix 3700. Currently server makers such as these must do without NUMA support or must create and support custom modifications to Linux. The recently accepted improvement should make it easier for server companies to build products and to attract customers.

The NUMA update was submitted by Martin Bligh, a Linux kernel programmer who works for IBM's Linux Technology Center. Bligh said in a posting to the Linux kernel mailing list that he has submitted NUMA updates to Torvalds before without success. However, his latest attempt used an approach that didn't affect Linux on non-NUMA computers, he said.

"These have been submitted...several times before, but in my opinion were structured in such a way to make them too invasive to non-NUMA machines," Bligh said, adding that NEC's Erich Focht did much of the work to restructure the software to make it noninvasive. "I believe these are now ready for mainline acceptance," he said, referring to its incorporation into standard Linux software.

Shortly after the submission was made, Torvalds posted that he accepted the NUMA software.

 

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