system-programming/06_AdvancedProcessManagement/README.md

📘 Chapter 6 – Advanced Process Management (Summary)

From Linux System Programming by Robert Love, 2nd Ed.

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🔄 Process Scheduling

• The kernel scheduler selects runnable processes (those not blocked on I/O, etc.).
• Goals: maximize CPU utilization, minimize wait time, and ensure fairness :contentReference[oaicite:1]{index=1}.
• Covers preemptive scheduling, timeslices, and the Linux Completely Fair Scheduler (CFS).
• Explains processor affinity and CPU sets: binding processes to specific CPUs for cache performance :contentReference[oaicite:2]{index=2}.

🧭 Yielding the Processor

• sched_yield() lets a running process give up the CPU voluntarily.
• Useful in busy-wait loops or when expecting immediate CPU from others :contentReference[oaicite:3]{index=3}.

🎚️ Priorities & Nice Values

• Processes can adjust their priority using nice(), where lower nice = higher priority.
• Real-time scheduling policies (SCHED_FIFO, SCHED_RR) grant stronger priority guarantees for time-sensitive tasks :contentReference[oaicite:4]{index=4}.

🧠 Processor Affinity

• Get/set CPU affinity with sched_getaffinity() and sched_setaffinity().
• Ensures cache affinity, reducing context-switch overhead :contentReference[oaicite:5]{index=5}.

⏱️ Real-Time Scheduling

• Differences between hard and soft real-time systems.
• Configurable policies: SCHED_FIFO, SCHED_RR, with real-time priority range 0–99 :contentReference[oaicite:6]{index=6}.
• Care needed: real-time tasks can lead to starvation of normal tasks.

🔒 Resource Limits

• Kernel enforces per-process limits via setrlimit()/getrlimit():
  • CPU usage (RLIMIT_CPU)
  • File sizes (RLIMIT_FSIZE)
  • Number of open files, memory, etc. :contentReference[oaicite:7]{index=7}.
• Helps contain rogue or misbehaving processes, essential for robustness.

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✅ Why It Matters

Advanced control over process scheduling, priorities, affinity, and resource limits is critical for writing:

• Real-time or latency-sensitive applications
• High-performance servers that benefit from core binding
• Robust daemons that avoid resource exhaustion

This chapter equips systems programmers with the tools to finely tune how tasks interact with the kernel scheduler and manage system impact.

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📚 References

• Linux System Programming, 2nd Ed. — Robert Love
• man 2 sched_setscheduler, man 2 setrlimit, man 2 sched_getaffinity
• Wikipedia: Completely Fair Scheduler :contentReference[oaicite:8]{index=8}