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The epoll API

Problems with Signal-driven I/O

• similar performance to epoll, but...
  
  
• Achieving full performance benefit requires Linux-specific feature, fcntl(F_SETSIG), to select a real-time signal for notification.
  
  
  • ues a queable real-time signal
  • siginfo_t argument passed to handler tells us which file descriptor is ready, and what event occurred.

  (i.e., requires non-portable extensions -- just as with epoll.).




• Dealing with signals is unnecessarily complex:
  
  
  • Signal handlers: must take care of race conditions, reentrancy issues, etc.
  • Accepting signals synchronously (sigwaitinfo()): signal queue overflow.
    
    



• Signals and threads do not mix well.
  
  
  
• Blunt instrument -- can't choose what kind of events to monitor

  (e.g., "read possible" versus "write possible").

(C) 2006, Michael Kerrisk