Will that run on an UltraSPARC T2?
By walterbays on Nov 11, 2007
Will a workload run well on a Sun SPARC Enterprise T5120, T5220, and Sun Blade T6320? The question has become easier to answer for the UltraSPARC T2 than it was for the UltraSPARC T1, which has limited floating point capability to match the majority of commercial workloads. However that means that for an UltraSPARC T1 you must be careful to ensure that your workload does not contain excessive floating point instructions.
By contrast the UltraSPARC T2 has enough floating point power to set the world record for single chip (Search form: enter "1 chip" in the "# CPU" field) SPECompM2001, the industry standard high performance computing benchmark for Open MP. Still with the T2 you need to determine whether your workload has sufficient parallelism to make effective use of the T2's 8 cores and 64 hardware threads. Back when we used to worry about using 64 CPU's in a Sun Enterprise 10000, the high performance computing community developed technologies like Open MP and MPI for portable expression of parallelism.
What's different today is those 64 virtual CPU's fitting into 1 RU of space, so we're looking at a much wider range of applications. Of course if you're consolidating multiple workloads onto a T2 based system using LDOMs or other virtualization method, then you already have those workloads running in parallel.
But what of the case where you want to mostly run a single application? If it's written in Java then it's likely to be multi-threaded, either because the language makes it natural to write the application that way, or because the utility classes called by the application are themselves multi-threaded. But a Java application might still be dominated by one or a few threads, and another application might be very well threaded.
The CoolThreads Selection Tool (cooltst) looks at the workload running on a system, and advises you about its suitability for T1 systems. As it happens, you can also use it to get an idea about the suitability of a workload for T2 systems - with some caveats. First, if you run cooltst on a T2 system it will complain that it doesn't know what processor it's running on; cooltst predates the T2 processor. But then you probably won't want to gauge the suitability of a workload already running on T2, to be migrated to a T2. Second, ignore anything it warns you about floating point content being too high for a T1; that isn't a problem for T2.
You can also just look at the workload yourself using standard Solaris (prstat) or Linux (top) commands, to see how the CPU consumption is spread across application threads. In upcoming blog entries I'll talk more about this simple do-it-yourself analysis.
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