Understanding Intel User Interrupts
Yves Kone, Louis Duval, Renaud Lachaize, Pascal A. Felber, Daniel Hagimont, Alain Tchana · Proceedings of the ACM on Measurement and Analysis of Computing Systems · 2025
User interrupts (UINTR) is a new hardware feature available in recent Intel Xeon processors. It enables a CPU to send, receive, and handle hardware inter-processor interrupts directly in user mode, meaning without the intervention of the OS kernel. In this paper, we shed light on the inner working of this facility and investigate, with detailed performance and overhead measurements considering deployments on physical machines and virtual machines with Linux and KVM, how it can be leveraged for more efficient inter-process communications, as an alternative to OS (Unix) signals. With UINTR, preemptive user-level thread schedulers can achieve quantum lengths in the microsecond scale.