The Problem: Giant Contention

• Contention in a Giant lock kernel occurs when tasks on multiple CPUs compete to enter the kernel

  • User threads performing system calls
  • Interrupt or timer driver kernel activity

• Occurs for workloads using kernel services

  • File system activity
  • Network activity
  • Misc. I/O activity
  • Inter-Process Communication (IPC)
  • Scheduler and context switches

• Also affects UP by limiting preemption