BigTux project shows Linux scaling to 64 processors

HP has demonstrated Linux running on 64 Itanium 2 processors without any loss of efficiency, and says it's seeing growing interest in open source from financial institutions

HP on Tuesday demonstrated Linux scaling to 64 processors on its Superdome hardware as it seeks to reassure customers who are increasingly considering the open source operating system for enterprise applications.

Running three different benchmarks on a standard Linux distribution based on the 2.6 kernel, the Superdome showed linear improvements for kernel compiling, memory bandwidth, and the HPL common supercomputer benchmark.

Operating system scalability is important to companies; without it, throwing more processors at a problem will result in diminishing returns. With OS scalability, doubling the number of processors should double the performance.

On the Superdome, demonstrated at HP's labs in Böblingen, Germany, a kernel compile using a single Itanium 2 processor took about 19 minutes (there are about 20,000 files to compile in this job).

Because the compile contained serial jobs, during which one processor intermittently collated the work, performance improved by a factor of 26 when all 64 Itanium 2 processors were used. With no serial jobs a performance improvement of 64 would have been expected, said Sebastien Cabaniols, engineering project leader on the project.

In the STREAM benchmark, memory bandwidth rose from 5GB/s with one 'cell' of four processors, to 10GB/s with two cells, and continued to double until all 64 processors -- or all 16 cells -- were switched on to provide 80GB/s of bandwidth.

The HPL benchmark, which is used to measure performance when solving large linear equations, produced similar results, rising from 18 gigaflops with one cell of four processors to 277 gigaflops with all 16 cells, or 64 processors, running.

"This was a standard Linux distribution," said Cabaniols. "The kernel was able to discover the topology of the system and discover the memory in a NUMA pattern."

NUMA, or 'non uniform memory architecture', refers to the cell-like architecture of the Superdome in which the 64 processors and their associated memory are split into 16 cells. In the demo machine half the 256GB of RAM was configured as local memory for the cells, and the other half was configured as pooled memory.

"The 2.6 kernel is NUMA aware," said Cabaniols. Some patching was necessary, he said, but "all patches developed for the BigTux project are going into the mainstream Linux kernel and are included in standard distributions."

Eva Beck, Linux business manager for HP Europe, said that in the past year and a half the company has seen customers using Linux for application servers. "Today it is a complete environment," she said, alluding to the use of Linux across all types of server, from Web servers and email servers to technical applications and now enterprise applications. "One the client side we're seeing a much stronger push too, prompted largely by the public sector installations," she added. "Banks and insurance companies are among those showing more interest in Linux on the desktop now."

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