Research on real-time Linux system modification and FPGA-based hardware-in-the-loop latency testing
With the increasing demand for operating system determinism in fields such as industrial automation and high-frequency trading, it is difficult for general-purpose Linux systems to meet microsecond-level control requirements due to the nonreal- time nature of their scheduling strategies. This paper proposes a Linux kernel real-time modification scheme based on the PREEMPT_RT patch and optimizes user-space system call overhead by combining VDSO (Virtual Dynamic Shared Object) technology. To overcome the limitations of pure software testing methods in terms of clock accuracy and system load interference, this paper innovatively designs a "Hardware-in-the-Loop" (HIL) latency testing method based on a PCIe interface FPGA board. This method uses the FPGA onboard 125MHz high-stability crystal oscillator as an independent time base to periodically read and verify the hardware counter through the kernel high-resolution timer, accurately quantifying the system scheduling jitter. Experimental results show that under the Fully Preemptible mode, the system's scheduling latency in multi-tasking loads is significantly reduced, meeting hard real-time application requirements.