To Pin or Not to Pin: Asserting the Scalability of QEMU Parallel Implementation

Due to its speed in cross-executing sequential code, dynamic binary translation is the unchallenged technology for full system-level simulation. Among the translators, QEMU has become the de facto solution. It introduced parallel host execution of the target cores a few years ago for the ARM instruction set architecture and this support is now also available, among others, for RISC-V. Given the popularity of these instruction sets in multi and many-core systems, assessing the scalability of their parallel implementation makes sense. In this paper, we use a subset of the PARSEC benchmark to measure the execution time of QEMU’s parallel implementation, to which we added the ability to pin a target processor to a host core or hardware thread. We report the results of a wealth of experiments we performed on a 16-core/32-thread x86-64 SMP machine. They show that the support of parallelism in QEMU scales well, and that, somewhat counter intuitively, pinning does not improve performance.