Will it run on multi-chip CMT?

April 15, 2008

Cooltst v3.0 is out, updated to assess workload suitability for single- and multi-chip CMT. When the UltraSPARC T1 was released, Cool Threads Selection Tool (cooltst) was developed to help gauge how well given workloads might run on the new chip which traded speed for throughput, allowing cooler, lower power, lower cost computing for many applications. But which applications? A single threaded application would tap just a tiny fraction of the 8 cores and 32 hardware threads of the UltraSPARC T1 processor.

Iguazu FallsMuch has changed since then. There is much empirical data showing various applications running well on CMT. The UltraSPARC T2 processor was released, increasing CMT power to 64 hardware threads. This processor also added dedicated floating point units per core so that, far from being relegated to a niche web server market, it claimed (and still holds) a high performance computing record.

Now UltraSPARC T2 Plus systems have been released, further extending CMT power to 2 chips, 8 cores per chip, 8 hardware threads per core – 128 virtual CPU’s in a 1RU box. Cooltst helps you assess how well your workload may tap that throughput potential. You can read about it and download it starting at sunsource.net.

There’s nothing magical about cooltst’s heuristics. You can make much the same assessment yourself using ordinary tools like ps (to look at the software threads) and cpustat (to look at instruction characteristics). All the source code is included so you can see what it’s doing. On Linux systems a loadable kernel module is included to measure instruction characteristics in place of Solaris’ built-in cpustat command. The output of cooltst is tabular data and a narrative description and  of your workload characteristics, and a bottom line recommendation.

Disclosure Statement:

SPEC and SPEComp are registered trademarks of Standard Performance Evaluation Corporation. Results are current as of 11/11/2007. Complete results may be found at the url referenced above or at http://www.spec.org/omp/results/ompm2001.html

My photo:

Iguazu Falls, on the border of Argentina and Brazil. It’s over twice as big as Niagara Falls in terms of water flow, because it covers such a wide area.