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PCIe Bandwidth Thrasher

Overview

The pcie_bandwidth test stresses the motherboard interconnect by forcing massive bidirectional transfers between the CPU and GPU. It detects bad riser cables, unstable PCIe generations (Gen4/Gen5), and driver timeouts.

Execution Mechanics

To hit peak Direct Memory Access (DMA) speeds, this kernel bypasses standard pageable memory.

  • It allocates "pinned" (page-locked) memory on the Host (CPU side).
  • It creates two independent execution streams to allow for asynchronous overlap.
  • The benchmark aggressively ping-pongs a large 256MB buffer, simultaneously executing Host-to-Device (H2D) and Device-to-Host (D2H) memory copies.

Target Subsystems

  • Primary Target: PCIe Bus Interface and Motherboard traces.
  • Secondary Target: CPU-side memory controller.

Failure Symptoms

Critical Failures

  • Low FPS / Stuttering: Dropping link speeds under load (e.g., falling from Gen4 x16 to Gen3 x8) due to physical degradation or poor mounting pressure.
  • Audio Crackling: PCIe bus contention causing interrupts on the host operating system.