Bernard Lint

Sequencer virtualization

The Multiple Instruction Stream Processor (MISP) architecture introduces the sequencer as a new class of architectural resource, and provides a minimalist user-level MIMD instruction set extension for application programs to directly control execution of concurrent instruction streams on these sequencers. As with classic architectural resources, namely, registers and memory, the sequencer architectural resource can be subject to virtualization. This paper details the idea of Sequencer Virtualization (SV), a foundational architectural support to decouple architectural virtual sequencers from physical sequencers. SV enables more efficient utilization of sequencer resources at the microarchitectural level while maintaining a consistent programming interface at the architectural level. To evaluate the key tradeoffs for SV, we conduct extensive experiments by implementing a prototype SV system using a custom firmware on a large-scale multiprocessor system. Using the prototype SV system, we demonstrate that SV improves efficiency in sequencer utilization while incurring little performance overhead. In particular, for a set of real multithreaded workloads, SV can significantly improve sequencer utilization, achieving an average of 32% better wall-clock performance than MISP without SV support in a multi-programming environment.