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Timers in Unix/Linux
The document discusses how timers work in Linux systems. There are two kernel counters that track time - one for seconds and one for microseconds since January 1, 1970. The gettimeofday function returns the current time by reading these counters. There are also per-process timers that track the time each process has spent running. A timer interrupt triggers every 10 milliseconds to increment the jiffies counter and schedule timer bottom half processing, which updates the system clock and process times. Processes can also initialize interval timers using setitimer to generate signals when the timers expire.
