Microarchitecture: A useful tool to organize machines in heterogeneous shared computing environments

Abstract

The x86_64 instruction set architecture is not a single, consistent, compatible interface to execute computer programs. Since the initial release in 1999, every new generation has added new instructions, some of which were later removed. Most of these new instructions are intended to improve the performance of those programs which explicitly take advantage of them. However, running such a program on older CPUs without appropriate support, results in Linux SIGILL exception signal, which is difficult for end users to diagnose. On the other hand, compiling scientific code for the least common denominator ISA can leave significant performance on the table. High Throughput systems, containing very large number of machines, cannot require a single CPU version across hundreds of thousands of machines operating in dozens of sites. The OSG Open Science Pool alone consists of more than 20 different, subtly incompatible X86_64 implementations. In 2020, Intel, AMD and RedHat proposed new terminology and partitioned these dozens of microarchitectures into a strict hierarchy of four groups. The HTCondor Software Suite and the OSG now have first class support for these microarchitectures. This paper discusses the advantages for users and future work around microarchitecture support.